diff options
Diffstat (limited to 'Documentation/technical')
20 files changed, 1271 insertions, 279 deletions
diff --git a/Documentation/technical/api-allocation-growing.txt b/Documentation/technical/api-allocation-growing.txt index 542946b1ba..5a59b54844 100644 --- a/Documentation/technical/api-allocation-growing.txt +++ b/Documentation/technical/api-allocation-growing.txt @@ -34,3 +34,6 @@ item[nr++] = value you like; ------------ You are responsible for updating the `nr` variable. + +If you need to specify the number of elements to allocate explicitly +then use the macro `REALLOC_ARRAY(item, alloc)` instead of `ALLOC_GROW`. diff --git a/Documentation/technical/api-argv-array.txt b/Documentation/technical/api-argv-array.txt index a6b7d83a8e..1a797812fb 100644 --- a/Documentation/technical/api-argv-array.txt +++ b/Documentation/technical/api-argv-array.txt @@ -53,11 +53,3 @@ Functions `argv_array_clear`:: Free all memory associated with the array and return it to the initial, empty state. - -`argv_array_detach`:: - Detach the argv array from the `struct argv_array`, transferring - ownership of the allocated array and strings. - -`argv_array_free_detached`:: - Free the memory allocated by a `struct argv_array` that was later - detached and is now no longer needed. diff --git a/Documentation/technical/api-builtin.txt b/Documentation/technical/api-builtin.txt index f3c1357b7c..22a39b9299 100644 --- a/Documentation/technical/api-builtin.txt +++ b/Documentation/technical/api-builtin.txt @@ -14,19 +14,22 @@ Git: . Add the external declaration for the function to `builtin.h`. -. Add the command to `commands[]` table in `handle_internal_command()`, - defined in `git.c`. The entry should look like: +. Add the command to the `commands[]` table defined in `git.c`. + The entry should look like: { "foo", cmd_foo, <options> }, + where options is the bitwise-or of: `RUN_SETUP`:: - - Make sure there is a Git directory to work on, and if there is a - work tree, chdir to the top of it if the command was invoked - in a subdirectory. If there is no work tree, no chdir() is - done. + If there is not a Git directory to work on, abort. If there + is a work tree, chdir to the top of it if the command was + invoked in a subdirectory. If there is no work tree, no + chdir() is done. + +`RUN_SETUP_GENTLY`:: + If there is a Git directory, chdir as per RUN_SETUP, otherwise, + don't chdir anywhere. `USE_PAGER`:: diff --git a/Documentation/technical/api-config.txt b/Documentation/technical/api-config.txt index 230b3a0f60..0d8b99b368 100644 --- a/Documentation/technical/api-config.txt +++ b/Documentation/technical/api-config.txt @@ -77,6 +77,99 @@ To read a specific file in git-config format, use `git_config_from_file`. This takes the same callback and data parameters as `git_config`. +Querying For Specific Variables +------------------------------- + +For programs wanting to query for specific variables in a non-callback +manner, the config API provides two functions `git_config_get_value` +and `git_config_get_value_multi`. They both read values from an internal +cache generated previously from reading the config files. + +`int git_config_get_value(const char *key, const char **value)`:: + + Finds the highest-priority value for the configuration variable `key`, + stores the pointer to it in `value` and returns 0. When the + configuration variable `key` is not found, returns 1 without touching + `value`. The caller should not free or modify `value`, as it is owned + by the cache. + +`const struct string_list *git_config_get_value_multi(const char *key)`:: + + Finds and returns the value list, sorted in order of increasing priority + for the configuration variable `key`. When the configuration variable + `key` is not found, returns NULL. The caller should not free or modify + the returned pointer, as it is owned by the cache. + +`void git_config_clear(void)`:: + + Resets and invalidates the config cache. + +The config API also provides type specific API functions which do conversion +as well as retrieval for the queried variable, including: + +`int git_config_get_int(const char *key, int *dest)`:: + + Finds and parses the value to an integer for the configuration variable + `key`. Dies on error; otherwise, stores the value of the parsed integer in + `dest` and returns 0. When the configuration variable `key` is not found, + returns 1 without touching `dest`. + +`int git_config_get_ulong(const char *key, unsigned long *dest)`:: + + Similar to `git_config_get_int` but for unsigned longs. + +`int git_config_get_bool(const char *key, int *dest)`:: + + Finds and parses the value into a boolean value, for the configuration + variable `key` respecting keywords like "true" and "false". Integer + values are converted into true/false values (when they are non-zero or + zero, respectively). Other values cause a die(). If parsing is successful, + stores the value of the parsed result in `dest` and returns 0. When the + configuration variable `key` is not found, returns 1 without touching + `dest`. + +`int git_config_get_bool_or_int(const char *key, int *is_bool, int *dest)`:: + + Similar to `git_config_get_bool`, except that integers are copied as-is, + and `is_bool` flag is unset. + +`int git_config_get_maybe_bool(const char *key, int *dest)`:: + + Similar to `git_config_get_bool`, except that it returns -1 on error + rather than dying. + +`int git_config_get_string_const(const char *key, const char **dest)`:: + + Allocates and copies the retrieved string into the `dest` parameter for + the configuration variable `key`; if NULL string is given, prints an + error message and returns -1. When the configuration variable `key` is + not found, returns 1 without touching `dest`. + +`int git_config_get_string(const char *key, char **dest)`:: + + Similar to `git_config_get_string_const`, except that retrieved value + copied into the `dest` parameter is a mutable string. + +`int git_config_get_pathname(const char *key, const char **dest)`:: + + Similar to `git_config_get_string`, but expands `~` or `~user` into + the user's home directory when found at the beginning of the path. + +`git_die_config(const char *key, const char *err, ...)`:: + + First prints the error message specified by the caller in `err` and then + dies printing the line number and the file name of the highest priority + value for the configuration variable `key`. + +`void git_die_config_linenr(const char *key, const char *filename, int linenr)`:: + + Helper function which formats the die error message according to the + parameters entered. Used by `git_die_config()`. It can be used by callers + handling `git_config_get_value_multi()` to print the correct error message + for the desired value. + +See test-config.c for usage examples. + Value Parsing Helpers --------------------- @@ -134,7 +227,98 @@ int read_file_with_include(const char *file, config_fn_t fn, void *data) `git_config` respects includes automatically. The lower-level `git_config_from_file` does not. +Custom Configsets +----------------- + +A `config_set` can be used to construct an in-memory cache for +config-like files that the caller specifies (i.e., files like `.gitmodules`, +`~/.gitconfig` etc.). For example, + +--------------------------------------- +struct config_set gm_config; +git_configset_init(&gm_config); +int b; +/* we add config files to the config_set */ +git_configset_add_file(&gm_config, ".gitmodules"); +git_configset_add_file(&gm_config, ".gitmodules_alt"); + +if (!git_configset_get_bool(gm_config, "submodule.frotz.ignore", &b)) { + /* hack hack hack */ +} + +/* when we are done with the configset */ +git_configset_clear(&gm_config); +---------------------------------------- + +Configset API provides functions for the above mentioned work flow, including: + +`void git_configset_init(struct config_set *cs)`:: + + Initializes the config_set `cs`. + +`int git_configset_add_file(struct config_set *cs, const char *filename)`:: + + Parses the file and adds the variable-value pairs to the `config_set`, + dies if there is an error in parsing the file. Returns 0 on success, or + -1 if the file does not exist or is inaccessible. The user has to decide + if he wants to free the incomplete configset or continue using it when + the function returns -1. + +`int git_configset_get_value(struct config_set *cs, const char *key, const char **value)`:: + + Finds the highest-priority value for the configuration variable `key` + and config set `cs`, stores the pointer to it in `value` and returns 0. + When the configuration variable `key` is not found, returns 1 without + touching `value`. The caller should not free or modify `value`, as it + is owned by the cache. + +`const struct string_list *git_configset_get_value_multi(struct config_set *cs, const char *key)`:: + + Finds and returns the value list, sorted in order of increasing priority + for the configuration variable `key` and config set `cs`. When the + configuration variable `key` is not found, returns NULL. The caller + should not free or modify the returned pointer, as it is owned by the cache. + +`void git_configset_clear(struct config_set *cs)`:: + + Clears `config_set` structure, removes all saved variable-value pairs. + +In addition to above functions, the `config_set` API provides type specific +functions in the vein of `git_config_get_int` and family but with an extra +parameter, pointer to struct `config_set`. +They all behave similarly to the `git_config_get*()` family described in +"Querying For Specific Variables" above. + Writing Config Files -------------------- -TODO +Git gives multiple entry points in the Config API to write config values to +files namely `git_config_set_in_file` and `git_config_set`, which write to +a specific config file or to `.git/config` respectively. They both take a +key/value pair as parameter. +In the end they both call `git_config_set_multivar_in_file` which takes four +parameters: + +- the name of the file, as a string, to which key/value pairs will be written. + +- the name of key, as a string. This is in canonical "flat" form: the section, + subsection, and variable segments will be separated by dots, and the section + and variable segments will be all lowercase. + E.g., `core.ignorecase`, `diff.SomeType.textconv`. + +- the value of the variable, as a string. If value is equal to NULL, it will + remove the matching key from the config file. + +- the value regex, as a string. It will disregard key/value pairs where value + does not match. + +- a multi_replace value, as an int. If value is equal to zero, nothing or only + one matching key/value is replaced, else all matching key/values (regardless + how many) are removed, before the new pair is written. + +It returns 0 on success. + +Also, there are functions `git_config_rename_section` and +`git_config_rename_section_in_file` with parameters `old_name` and `new_name` +for renaming or removing sections in the config files. If NULL is passed +through `new_name` parameter, the section will be removed from the config file. diff --git a/Documentation/technical/api-gitattributes.txt b/Documentation/technical/api-gitattributes.txt index ce363b6305..2602668677 100644 --- a/Documentation/technical/api-gitattributes.txt +++ b/Documentation/technical/api-gitattributes.txt @@ -99,7 +99,7 @@ static void setup_check(void) The attribute is Unset, by listing the name of the attribute prefixed with a dash - for the path. } else if (ATTR_UNSET(value)) { - The attribute is not set nor unset for the path. + The attribute is neither set nor unset for the path. } else if (!strcmp(value, "input")) { If none of ATTR_TRUE(), ATTR_FALSE(), or ATTR_UNSET() is true, the value is a string set in the gitattributes diff --git a/Documentation/technical/api-hash.txt b/Documentation/technical/api-hash.txt deleted file mode 100644 index e5061e0677..0000000000 --- a/Documentation/technical/api-hash.txt +++ /dev/null @@ -1,52 +0,0 @@ -hash API -======== - -The hash API is a collection of simple hash table functions. Users are expected -to implement their own hashing. - -Data Structures ---------------- - -`struct hash_table`:: - - The hash table structure. The `array` member points to the hash table - entries. The `size` member counts the total number of valid and invalid - entries in the table. The `nr` member keeps track of the number of - valid entries. - -`struct hash_table_entry`:: - - An opaque structure representing an entry in the hash table. The `hash` - member is the entry's hash key and the `ptr` member is the entry's - value. - -Functions ---------- - -`init_hash`:: - - Initialize the hash table. - -`free_hash`:: - - Release memory associated with the hash table. - -`insert_hash`:: - - Insert a pointer into the hash table. If an entry with that hash - already exists, a pointer to the existing entry's value is returned. - Otherwise NULL is returned. This allows callers to implement - chaining, etc. - -`lookup_hash`:: - - Lookup an entry in the hash table. If an entry with that hash exists - the entry's value is returned. Otherwise NULL is returned. - -`for_each_hash`:: - - Call a function for each entry in the hash table. The function is - expected to take the entry's value as its only argument and return an - int. If the function returns a negative int the loop is aborted - immediately. Otherwise, the return value is accumulated and the sum - returned upon completion of the loop. diff --git a/Documentation/technical/api-hashmap.txt b/Documentation/technical/api-hashmap.txt new file mode 100644 index 0000000000..ad7a5bddd2 --- /dev/null +++ b/Documentation/technical/api-hashmap.txt @@ -0,0 +1,280 @@ +hashmap API +=========== + +The hashmap API is a generic implementation of hash-based key-value mappings. + +Data Structures +--------------- + +`struct hashmap`:: + + The hash table structure. Members can be used as follows, but should + not be modified directly: ++ +The `size` member keeps track of the total number of entries (0 means the +hashmap is empty). ++ +`tablesize` is the allocated size of the hash table. A non-0 value indicates +that the hashmap is initialized. It may also be useful for statistical purposes +(i.e. `size / tablesize` is the current load factor). ++ +`cmpfn` stores the comparison function specified in `hashmap_init()`. In +advanced scenarios, it may be useful to change this, e.g. to switch between +case-sensitive and case-insensitive lookup. + +`struct hashmap_entry`:: + + An opaque structure representing an entry in the hash table, which must + be used as first member of user data structures. Ideally it should be + followed by an int-sized member to prevent unused memory on 64-bit + systems due to alignment. ++ +The `hash` member is the entry's hash code and the `next` member points to the +next entry in case of collisions (i.e. if multiple entries map to the same +bucket). + +`struct hashmap_iter`:: + + An iterator structure, to be used with hashmap_iter_* functions. + +Types +----- + +`int (*hashmap_cmp_fn)(const void *entry, const void *entry_or_key, const void *keydata)`:: + + User-supplied function to test two hashmap entries for equality. Shall + return 0 if the entries are equal. ++ +This function is always called with non-NULL `entry` / `entry_or_key` +parameters that have the same hash code. When looking up an entry, the `key` +and `keydata` parameters to hashmap_get and hashmap_remove are always passed +as second and third argument, respectively. Otherwise, `keydata` is NULL. + +Functions +--------- + +`unsigned int strhash(const char *buf)`:: +`unsigned int strihash(const char *buf)`:: +`unsigned int memhash(const void *buf, size_t len)`:: +`unsigned int memihash(const void *buf, size_t len)`:: + + Ready-to-use hash functions for strings, using the FNV-1 algorithm (see + http://www.isthe.com/chongo/tech/comp/fnv). ++ +`strhash` and `strihash` take 0-terminated strings, while `memhash` and +`memihash` operate on arbitrary-length memory. ++ +`strihash` and `memihash` are case insensitive versions. + +`unsigned int sha1hash(const unsigned char *sha1)`:: + + Converts a cryptographic hash (e.g. SHA-1) into an int-sized hash code + for use in hash tables. Cryptographic hashes are supposed to have + uniform distribution, so in contrast to `memhash()`, this just copies + the first `sizeof(int)` bytes without shuffling any bits. Note that + the results will be different on big-endian and little-endian + platforms, so they should not be stored or transferred over the net. + +`void hashmap_init(struct hashmap *map, hashmap_cmp_fn equals_function, size_t initial_size)`:: + + Initializes a hashmap structure. ++ +`map` is the hashmap to initialize. ++ +The `equals_function` can be specified to compare two entries for equality. +If NULL, entries are considered equal if their hash codes are equal. ++ +If the total number of entries is known in advance, the `initial_size` +parameter may be used to preallocate a sufficiently large table and thus +prevent expensive resizing. If 0, the table is dynamically resized. + +`void hashmap_free(struct hashmap *map, int free_entries)`:: + + Frees a hashmap structure and allocated memory. ++ +`map` is the hashmap to free. ++ +If `free_entries` is true, each hashmap_entry in the map is freed as well +(using stdlib's free()). + +`void hashmap_entry_init(void *entry, unsigned int hash)`:: + + Initializes a hashmap_entry structure. ++ +`entry` points to the entry to initialize. ++ +`hash` is the hash code of the entry. + +`void *hashmap_get(const struct hashmap *map, const void *key, const void *keydata)`:: + + Returns the hashmap entry for the specified key, or NULL if not found. ++ +`map` is the hashmap structure. ++ +`key` is a hashmap_entry structure (or user data structure that starts with +hashmap_entry) that has at least been initialized with the proper hash code +(via `hashmap_entry_init`). ++ +If an entry with matching hash code is found, `key` and `keydata` are passed +to `hashmap_cmp_fn` to decide whether the entry matches the key. + +`void *hashmap_get_from_hash(const struct hashmap *map, unsigned int hash, const void *keydata)`:: + + Returns the hashmap entry for the specified hash code and key data, + or NULL if not found. ++ +`map` is the hashmap structure. ++ +`hash` is the hash code of the entry to look up. ++ +If an entry with matching hash code is found, `keydata` is passed to +`hashmap_cmp_fn` to decide whether the entry matches the key. The +`entry_or_key` parameter points to a bogus hashmap_entry structure that +should not be used in the comparison. + +`void *hashmap_get_next(const struct hashmap *map, const void *entry)`:: + + Returns the next equal hashmap entry, or NULL if not found. This can be + used to iterate over duplicate entries (see `hashmap_add`). ++ +`map` is the hashmap structure. ++ +`entry` is the hashmap_entry to start the search from, obtained via a previous +call to `hashmap_get` or `hashmap_get_next`. + +`void hashmap_add(struct hashmap *map, void *entry)`:: + + Adds a hashmap entry. This allows to add duplicate entries (i.e. + separate values with the same key according to hashmap_cmp_fn). ++ +`map` is the hashmap structure. ++ +`entry` is the entry to add. + +`void *hashmap_put(struct hashmap *map, void *entry)`:: + + Adds or replaces a hashmap entry. If the hashmap contains duplicate + entries equal to the specified entry, only one of them will be replaced. ++ +`map` is the hashmap structure. ++ +`entry` is the entry to add or replace. ++ +Returns the replaced entry, or NULL if not found (i.e. the entry was added). + +`void *hashmap_remove(struct hashmap *map, const void *key, const void *keydata)`:: + + Removes a hashmap entry matching the specified key. If the hashmap + contains duplicate entries equal to the specified key, only one of + them will be removed. ++ +`map` is the hashmap structure. ++ +`key` is a hashmap_entry structure (or user data structure that starts with +hashmap_entry) that has at least been initialized with the proper hash code +(via `hashmap_entry_init`). ++ +If an entry with matching hash code is found, `key` and `keydata` are +passed to `hashmap_cmp_fn` to decide whether the entry matches the key. ++ +Returns the removed entry, or NULL if not found. + +`void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter)`:: +`void *hashmap_iter_next(struct hashmap_iter *iter)`:: +`void *hashmap_iter_first(struct hashmap *map, struct hashmap_iter *iter)`:: + + Used to iterate over all entries of a hashmap. ++ +`hashmap_iter_init` initializes a `hashmap_iter` structure. ++ +`hashmap_iter_next` returns the next hashmap_entry, or NULL if there are no +more entries. ++ +`hashmap_iter_first` is a combination of both (i.e. initializes the iterator +and returns the first entry, if any). + +`const char *strintern(const char *string)`:: +`const void *memintern(const void *data, size_t len)`:: + + Returns the unique, interned version of the specified string or data, + similar to the `String.intern` API in Java and .NET, respectively. + Interned strings remain valid for the entire lifetime of the process. ++ +Can be used as `[x]strdup()` or `xmemdupz` replacement, except that interned +strings / data must not be modified or freed. ++ +Interned strings are best used for short strings with high probability of +duplicates. ++ +Uses a hashmap to store the pool of interned strings. + +Usage example +------------- + +Here's a simple usage example that maps long keys to double values. +------------ +struct hashmap map; + +struct long2double { + struct hashmap_entry ent; /* must be the first member! */ + long key; + double value; +}; + +static int long2double_cmp(const struct long2double *e1, const struct long2double *e2, const void *unused) +{ + return !(e1->key == e2->key); +} + +void long2double_init(void) +{ + hashmap_init(&map, (hashmap_cmp_fn) long2double_cmp, 0); +} + +void long2double_free(void) +{ + hashmap_free(&map, 1); +} + +static struct long2double *find_entry(long key) +{ + struct long2double k; + hashmap_entry_init(&k, memhash(&key, sizeof(long))); + k.key = key; + return hashmap_get(&map, &k, NULL); +} + +double get_value(long key) +{ + struct long2double *e = find_entry(key); + return e ? e->value : 0; +} + +void set_value(long key, double value) +{ + struct long2double *e = find_entry(key); + if (!e) { + e = malloc(sizeof(struct long2double)); + hashmap_entry_init(e, memhash(&key, sizeof(long))); + e->key = key; + hashmap_add(&map, e); + } + e->value = value; +} +------------ + +Using variable-sized keys +------------------------- + +The `hashmap_entry_get` and `hashmap_entry_remove` functions expect an ordinary +`hashmap_entry` structure as key to find the correct entry. If the key data is +variable-sized (e.g. a FLEX_ARRAY string) or quite large, it is undesirable +to create a full-fledged entry structure on the heap and copy all the key data +into the structure. + +In this case, the `keydata` parameter can be used to pass +variable-sized key data directly to the comparison function, and the `key` +parameter can be a stripped-down, fixed size entry structure allocated on the +stack. + +See test-hashmap.c for an example using arbitrary-length strings as keys. diff --git a/Documentation/technical/api-lockfile.txt b/Documentation/technical/api-lockfile.txt index dd894043ae..93b5f23e4c 100644 --- a/Documentation/technical/api-lockfile.txt +++ b/Documentation/technical/api-lockfile.txt @@ -3,20 +3,132 @@ lockfile API The lockfile API serves two purposes: -* Mutual exclusion. When we write out a new index file, first - we create a new file `$GIT_DIR/index.lock`, write the new - contents into it, and rename it to the final destination - `$GIT_DIR/index`. We try to create the `$GIT_DIR/index.lock` - file with O_EXCL so that we can notice and fail when somebody - else is already trying to update the index file. - -* Automatic cruft removal. After we create the "lock" file, we - may decide to `die()`, and we would want to make sure that we - remove the file that has not been committed to its final - destination. This is done by remembering the lockfiles we - created in a linked list and cleaning them up from an - `atexit(3)` handler. Outstanding lockfiles are also removed - when the program dies on a signal. +* Mutual exclusion and atomic file updates. When we want to change a + file, we create a lockfile `<filename>.lock`, write the new file + contents into it, and then rename the lockfile to its final + destination `<filename>`. We create the `<filename>.lock` file with + `O_CREAT|O_EXCL` so that we can notice and fail if somebody else has + already locked the file, then atomically rename the lockfile to its + final destination to commit the changes and unlock the file. + +* Automatic cruft removal. If the program exits after we lock a file + but before the changes have been committed, we want to make sure + that we remove the lockfile. This is done by remembering the + lockfiles we have created in a linked list and setting up an + `atexit(3)` handler and a signal handler that clean up the + lockfiles. This mechanism ensures that outstanding lockfiles are + cleaned up if the program exits (including when `die()` is called) + or if the program dies on a signal. + +Please note that lockfiles only block other writers. Readers do not +block, but they are guaranteed to see either the old contents of the +file or the new contents of the file (assuming that the filesystem +implements `rename(2)` atomically). + + +Calling sequence +---------------- + +The caller: + +* Allocates a `struct lock_file` either as a static variable or on the + heap, initialized to zeros. Once you use the structure to call the + `hold_lock_file_*` family of functions, it belongs to the lockfile + subsystem and its storage must remain valid throughout the life of + the program (i.e. you cannot use an on-stack variable to hold this + structure). + +* Attempts to create a lockfile by passing that variable and the path + of the final destination (e.g. `$GIT_DIR/index`) to + `hold_lock_file_for_update` or `hold_lock_file_for_append`. + +* Writes new content for the destination file by either: + + * writing to the file descriptor returned by the `hold_lock_file_*` + functions (also available via `lock->fd`). + + * calling `fdopen_lock_file` to get a `FILE` pointer for the open + file and writing to the file using stdio. + +When finished writing, the caller can: + +* Close the file descriptor and rename the lockfile to its final + destination by calling `commit_lock_file` or `commit_lock_file_to`. + +* Close the file descriptor and remove the lockfile by calling + `rollback_lock_file`. + +* Close the file descriptor without removing or renaming the lockfile + by calling `close_lock_file`, and later call `commit_lock_file`, + `commit_lock_file_to`, `rollback_lock_file`, or `reopen_lock_file`. + +Even after the lockfile is committed or rolled back, the `lock_file` +object must not be freed or altered by the caller. However, it may be +reused; just pass it to another call of `hold_lock_file_for_update` or +`hold_lock_file_for_append`. + +If the program exits before you have called one of `commit_lock_file`, +`commit_lock_file_to`, `rollback_lock_file`, or `close_lock_file`, an +`atexit(3)` handler will close and remove the lockfile, rolling back +any uncommitted changes. + +If you need to close the file descriptor you obtained from a +`hold_lock_file_*` function yourself, do so by calling +`close_lock_file`. You should never call `close(2)` or `fclose(3)` +yourself! Otherwise the `struct lock_file` structure would still think +that the file descriptor needs to be closed, and a commit or rollback +would result in duplicate calls to `close(2)`. Worse yet, if you close +and then later open another file descriptor for a completely different +purpose, then a commit or rollback might close that unrelated file +descriptor. + + +Error handling +-------------- + +The `hold_lock_file_*` functions return a file descriptor on success +or -1 on failure (unless `LOCK_DIE_ON_ERROR` is used; see below). On +errors, `errno` describes the reason for failure. Errors can be +reported by passing `errno` to one of the following helper functions: + +unable_to_lock_message:: + + Append an appropriate error message to a `strbuf`. + +unable_to_lock_error:: + + Emit an appropriate error message using `error()`. + +unable_to_lock_die:: + + Emit an appropriate error message and `die()`. + +Similarly, `commit_lock_file`, `commit_lock_file_to`, and +`close_lock_file` return 0 on success. On failure they set `errno` +appropriately, do their best to roll back the lockfile, and return -1. + + +Flags +----- + +The following flags can be passed to `hold_lock_file_for_update` or +`hold_lock_file_for_append`: + +LOCK_NO_DEREF:: + + Usually symbolic links in the destination path are resolved + and the lockfile is created by adding ".lock" to the resolved + path. If `LOCK_NO_DEREF` is set, then the lockfile is created + by adding ".lock" to the path argument itself. This option is + used, for example, when locking a symbolic reference, which + for backwards-compatibility reasons can be a symbolic link + containing the name of the referred-to-reference. + +LOCK_DIE_ON_ERROR:: + + If a lock is already taken for the file, `die()` with an error + message. If this option is not specified, trying to lock a + file that is already locked returns -1 to the caller. The functions @@ -24,51 +136,85 @@ The functions hold_lock_file_for_update:: - Take a pointer to `struct lock_file`, the filename of - the final destination (e.g. `$GIT_DIR/index`) and a flag - `die_on_error`. Attempt to create a lockfile for the - destination and return the file descriptor for writing - to the file. If `die_on_error` flag is true, it dies if - a lock is already taken for the file; otherwise it - returns a negative integer to the caller on failure. + Take a pointer to `struct lock_file`, the path of the file to + be locked (e.g. `$GIT_DIR/index`) and a flags argument (see + above). Attempt to create a lockfile for the destination and + return the file descriptor for writing to the file. + +hold_lock_file_for_append:: + + Like `hold_lock_file_for_update`, but before returning copy + the existing contents of the file (if any) to the lockfile and + position its write pointer at the end of the file. + +fdopen_lock_file:: + + Associate a stdio stream with the lockfile. Return NULL + (*without* rolling back the lockfile) on error. The stream is + closed automatically when `close_lock_file` is called or when + the file is committed or rolled back. + +get_locked_file_path:: + + Return the path of the file that is locked by the specified + lock_file object. The caller must free the memory. commit_lock_file:: - Take a pointer to the `struct lock_file` initialized - with an earlier call to `hold_lock_file_for_update()`, - close the file descriptor and rename the lockfile to its - final destination. Returns 0 upon success, a negative - value on failure to close(2) or rename(2). + Take a pointer to the `struct lock_file` initialized with an + earlier call to `hold_lock_file_for_update` or + `hold_lock_file_for_append`, close the file descriptor, and + rename the lockfile to its final destination. Return 0 upon + success. On failure, roll back the lock file and return -1, + with `errno` set to the value from the failing call to + `close(2)` or `rename(2)`. It is a bug to call + `commit_lock_file` for a `lock_file` object that is not + currently locked. + +commit_lock_file_to:: + + Like `commit_lock_file()`, except that it takes an explicit + `path` argument to which the lockfile should be renamed. The + `path` must be on the same filesystem as the lock file. rollback_lock_file:: - Take a pointer to the `struct lock_file` initialized - with an earlier call to `hold_lock_file_for_update()`, - close the file descriptor and remove the lockfile. + Take a pointer to the `struct lock_file` initialized with an + earlier call to `hold_lock_file_for_update` or + `hold_lock_file_for_append`, close the file descriptor and + remove the lockfile. It is a NOOP to call + `rollback_lock_file()` for a `lock_file` object that has + already been committed or rolled back. close_lock_file:: - Take a pointer to the `struct lock_file` initialized - with an earlier call to `hold_lock_file_for_update()`, - and close the file descriptor. Returns 0 upon success, - a negative value on failure to close(2). - -Because the structure is used in an `atexit(3)` handler, its -storage has to stay throughout the life of the program. It -cannot be an auto variable allocated on the stack. - -Call `commit_lock_file()` or `rollback_lock_file()` when you are -done writing to the file descriptor. If you do not call either -and simply `exit(3)` from the program, an `atexit(3)` handler -will close and remove the lockfile. - -If you need to close the file descriptor you obtained from -`hold_lock_file_for_update` function yourself, do so by calling -`close_lock_file()`. You should never call `close(2)` yourself! -Otherwise the `struct -lock_file` structure still remembers that the file descriptor -needs to be closed, and a later call to `commit_lock_file()` or -`rollback_lock_file()` will result in duplicate calls to -`close(2)`. Worse yet, if you `close(2)`, open another file -descriptor for completely different purpose, and then call -`commit_lock_file()` or `rollback_lock_file()`, they may close -that unrelated file descriptor. + + Take a pointer to the `struct lock_file` initialized with an + earlier call to `hold_lock_file_for_update` or + `hold_lock_file_for_append`. Close the file descriptor (and + the file pointer if it has been opened using + `fdopen_lock_file`). Return 0 upon success. On failure to + `close(2)`, return a negative value and roll back the lock + file. Usually `commit_lock_file`, `commit_lock_file_to`, or + `rollback_lock_file` should eventually be called if + `close_lock_file` succeeds. + +reopen_lock_file:: + + Re-open a lockfile that has been closed (using + `close_lock_file`) but not yet committed or rolled back. This + can be used to implement a sequence of operations like the + following: + + * Lock file. + + * Write new contents to lockfile, then `close_lock_file` to + cause the contents to be written to disk. + + * Pass the name of the lockfile to another program to allow it + (and nobody else) to inspect the contents you wrote, while + still holding the lock yourself. + + * `reopen_lock_file` to reopen the lockfile. Make further + updates to the contents. + + * `commit_lock_file` to make the final version permanent. diff --git a/Documentation/technical/api-parse-options.txt b/Documentation/technical/api-parse-options.txt index 0be2b5159f..1f2db31312 100644 --- a/Documentation/technical/api-parse-options.txt +++ b/Documentation/technical/api-parse-options.txt @@ -29,9 +29,9 @@ that allow to change the behavior of a command. The parse-options API allows: -* 'sticked' and 'separate form' of options with arguments. - `-oArg` is sticked, `-o Arg` is separate form. - `--option=Arg` is sticked, `--option Arg` is separate form. +* 'stuck' and 'separate form' of options with arguments. + `-oArg` is stuck, `-o Arg` is separate form. + `--option=Arg` is stuck, `--option Arg` is separate form. * Long options may be 'abbreviated', as long as the abbreviation is unambiguous. @@ -160,10 +160,6 @@ There are some macros to easily define options: `int_var` is set to `integer` with `--option`, and reset to zero with `--no-option`. -`OPT_SET_PTR(short, long, &ptr_var, description, ptr)`:: - Introduce a boolean option. - If used, set `ptr_var` to `ptr`. - `OPT_STRING(short, long, &str_var, arg_str, description)`:: Introduce an option with string argument. The string argument is put into `str_var`. diff --git a/Documentation/technical/api-remote.txt b/Documentation/technical/api-remote.txt index 4be87768f6..5d245aa9d1 100644 --- a/Documentation/technical/api-remote.txt +++ b/Documentation/technical/api-remote.txt @@ -58,16 +58,16 @@ default remote, given the current branch and configuration. struct refspec -------------- -A struct refspec holds the parsed interpretation of a refspec. If it -will force updates (starts with a '+'), force is true. If it is a -pattern (sides end with '*') pattern is true. src and dest are the two -sides (if a pattern, only the part outside of the wildcards); if there -is only one side, it is src, and dst is NULL; if sides exist but are -empty (i.e., the refspec either starts or ends with ':'), the -corresponding side is "". - -This parsing can be done to an array of strings to give an array of -struct refpsecs with parse_ref_spec(). +A struct refspec holds the parsed interpretation of a refspec. If it +will force updates (starts with a '+'), force is true. If it is a +pattern (sides end with '*') pattern is true. src and dest are the +two sides (including '*' characters if present); if there is only one +side, it is src, and dst is NULL; if sides exist but are empty (i.e., +the refspec either starts or ends with ':'), the corresponding side is +"". + +An array of strings can be parsed into an array of struct refspecs +using parse_fetch_refspec() or parse_push_refspec(). remote_find_tracking(), given a remote and a struct refspec with either src or dst filled out, will fill out the other such that the diff --git a/Documentation/technical/api-run-command.txt b/Documentation/technical/api-run-command.txt index 5d7d7f2d32..842b8389eb 100644 --- a/Documentation/technical/api-run-command.txt +++ b/Documentation/technical/api-run-command.txt @@ -13,6 +13,10 @@ produces in the caller in order to process it. Functions --------- +`child_process_init` + + Initialize a struct child_process variable. + `start_command`:: Start a sub-process. Takes a pointer to a `struct child_process` @@ -96,8 +100,8 @@ command to run in a sub-process. The caller: -1. allocates and clears (memset(&chld, 0, sizeof(chld));) a - struct child_process variable; +1. allocates and clears (using child_process_init() or + CHILD_PROCESS_INIT) a struct child_process variable; 2. initializes the members; 3. calls start_command(); 4. processes the data; @@ -109,6 +113,13 @@ terminated), of which .argv[0] is the program name to run (usually without a path). If the command to run is a git command, set argv[0] to the command name without the 'git-' prefix and set .git_cmd = 1. +Note that the ownership of the memory pointed to by .argv stays with the +caller, but it should survive until `finish_command` completes. If the +.argv member is NULL, `start_command` will point it at the .args +`argv_array` (so you may use one or the other, but you must use exactly +one). The memory in .args will be cleaned up automatically during +`finish_command` (or during `start_command` when it is unsuccessful). + The members .in, .out, .err are used to redirect stdin, stdout, stderr as follows: diff --git a/Documentation/technical/api-strbuf.txt b/Documentation/technical/api-strbuf.txt index 3350d97dda..cca6543234 100644 --- a/Documentation/technical/api-strbuf.txt +++ b/Documentation/technical/api-strbuf.txt @@ -7,10 +7,10 @@ use the mem* functions than a str* one (memchr vs. strchr e.g.). Though, one has to be careful about the fact that str* functions often stop on NULs and that strbufs may have embedded NULs. -An strbuf is NUL terminated for convenience, but no function in the +A strbuf is NUL terminated for convenience, but no function in the strbuf API actually relies on the string being free of NULs. -strbufs has some invariants that are very important to keep in mind: +strbufs have some invariants that are very important to keep in mind: . The `buf` member is never NULL, so it can be used in any usual C string operations safely. strbuf's _have_ to be initialized either by @@ -56,8 +56,8 @@ Data structures * `struct strbuf` This is the string buffer structure. The `len` member can be used to -determine the current length of the string, and `buf` member provides access to -the string itself. +determine the current length of the string, and `buf` member provides +access to the string itself. Functions --------- @@ -121,10 +121,28 @@ Functions * Related to the contents of the buffer +`strbuf_trim`:: + + Strip whitespace from the beginning and end of a string. + Equivalent to performing `strbuf_rtrim()` followed by `strbuf_ltrim()`. + `strbuf_rtrim`:: Strip whitespace from the end of a string. +`strbuf_ltrim`:: + + Strip whitespace from the beginning of a string. + +`strbuf_reencode`:: + + Replace the contents of the strbuf with a reencoded form. Returns -1 + on error, 0 on success. + +`strbuf_tolower`:: + + Lowercase each character in the buffer using `tolower`. + `strbuf_cmp`:: Compare two buffers. Returns an integer less than, equal to, or greater @@ -142,6 +160,10 @@ then they will free() it. Add a single character to the buffer. +`strbuf_addchars`:: + + Add a character the specified number of times to the buffer. + `strbuf_insert`:: Insert data to the given position of the buffer. The remaining contents @@ -184,7 +206,7 @@ strbuf_addstr(sb, "immediate string"); `strbuf_addbuf`:: - Copy the contents of an other buffer at the end of the current one. + Copy the contents of another buffer at the end of the current one. `strbuf_adddup`:: @@ -289,6 +311,16 @@ same behaviour as well. use it unless you need the correct position in the file descriptor. +`strbuf_getcwd`:: + + Set the buffer to the path of the current working directory. + +`strbuf_add_absolute_path` + + Add a path to a buffer, converting a relative path to an + absolute one in the process. Symbolic links are not + resolved. + `stripspace`:: Strip whitespace from a buffer. The second parameter controls if diff --git a/Documentation/technical/api-string-list.txt b/Documentation/technical/api-string-list.txt index 20be348834..d51a6579c8 100644 --- a/Documentation/technical/api-string-list.txt +++ b/Documentation/technical/api-string-list.txt @@ -68,6 +68,11 @@ Functions * General ones (works with sorted and unsorted lists as well) +`string_list_init`:: + + Initialize the members of the string_list, set `strdup_strings` + member according to the value of the second parameter. + `filter_string_list`:: Apply a function to each item in a list, retaining only the @@ -200,3 +205,5 @@ Represents the list itself. You should not tamper with it. . Setting the `strdup_strings` member to 1 will strdup() the strings before adding them, see above. +. The `compare_strings_fn` member is used to specify a custom compare + function, otherwise `strcmp()` is used as the default function. diff --git a/Documentation/technical/api-trace.txt b/Documentation/technical/api-trace.txt new file mode 100644 index 0000000000..097a651d96 --- /dev/null +++ b/Documentation/technical/api-trace.txt @@ -0,0 +1,97 @@ +trace API +========= + +The trace API can be used to print debug messages to stderr or a file. Trace +code is inactive unless explicitly enabled by setting `GIT_TRACE*` environment +variables. + +The trace implementation automatically adds `timestamp file:line ... \n` to +all trace messages. E.g.: + +------------ +23:59:59.123456 git.c:312 trace: built-in: git 'foo' +00:00:00.000001 builtin/foo.c:99 foo: some message +------------ + +Data Structures +--------------- + +`struct trace_key`:: + + Defines a trace key (or category). The default (for API functions that + don't take a key) is `GIT_TRACE`. ++ +E.g. to define a trace key controlled by environment variable `GIT_TRACE_FOO`: ++ +------------ +static struct trace_key trace_foo = TRACE_KEY_INIT(FOO); + +static void trace_print_foo(const char *message) +{ + trace_print_key(&trace_foo, message); +} +------------ ++ +Note: don't use `const` as the trace implementation stores internal state in +the `trace_key` structure. + +Functions +--------- + +`int trace_want(struct trace_key *key)`:: + + Checks whether the trace key is enabled. Used to prevent expensive + string formatting before calling one of the printing APIs. + +`void trace_disable(struct trace_key *key)`:: + + Disables tracing for the specified key, even if the environment + variable was set. + +`void trace_printf(const char *format, ...)`:: +`void trace_printf_key(struct trace_key *key, const char *format, ...)`:: + + Prints a formatted message, similar to printf. + +`void trace_argv_printf(const char **argv, const char *format, ...)``:: + + Prints a formatted message, followed by a quoted list of arguments. + +`void trace_strbuf(struct trace_key *key, const struct strbuf *data)`:: + + Prints the strbuf, without additional formatting (i.e. doesn't + choke on `%` or even `\0`). + +`uint64_t getnanotime(void)`:: + + Returns nanoseconds since the epoch (01/01/1970), typically used + for performance measurements. ++ +Currently there are high precision timer implementations for Linux (using +`clock_gettime(CLOCK_MONOTONIC)`) and Windows (`QueryPerformanceCounter`). +Other platforms use `gettimeofday` as time source. + +`void trace_performance(uint64_t nanos, const char *format, ...)`:: +`void trace_performance_since(uint64_t start, const char *format, ...)`:: + + Prints the elapsed time (in nanoseconds), or elapsed time since + `start`, followed by a formatted message. Enabled via environment + variable `GIT_TRACE_PERFORMANCE`. Used for manual profiling, e.g.: ++ +------------ +uint64_t start = getnanotime(); +/* code section to measure */ +trace_performance_since(start, "foobar"); +------------ ++ +------------ +uint64_t t = 0; +for (;;) { + /* ignore */ + t -= getnanotime(); + /* code section to measure */ + t += getnanotime(); + /* ignore */ +} +trace_performance(t, "frotz"); +------------ diff --git a/Documentation/technical/bitmap-format.txt b/Documentation/technical/bitmap-format.txt new file mode 100644 index 0000000000..f8c18a0f7a --- /dev/null +++ b/Documentation/technical/bitmap-format.txt @@ -0,0 +1,164 @@ +GIT bitmap v1 format +==================== + + - A header appears at the beginning: + + 4-byte signature: {'B', 'I', 'T', 'M'} + + 2-byte version number (network byte order) + The current implementation only supports version 1 + of the bitmap index (the same one as JGit). + + 2-byte flags (network byte order) + + The following flags are supported: + + - BITMAP_OPT_FULL_DAG (0x1) REQUIRED + This flag must always be present. It implies that the bitmap + index has been generated for a packfile with full closure + (i.e. where every single object in the packfile can find + its parent links inside the same packfile). This is a + requirement for the bitmap index format, also present in JGit, + that greatly reduces the complexity of the implementation. + + - BITMAP_OPT_HASH_CACHE (0x4) + If present, the end of the bitmap file contains + `N` 32-bit name-hash values, one per object in the + pack. The format and meaning of the name-hash is + described below. + + 4-byte entry count (network byte order) + + The total count of entries (bitmapped commits) in this bitmap index. + + 20-byte checksum + + The SHA1 checksum of the pack this bitmap index belongs to. + + - 4 EWAH bitmaps that act as type indexes + + Type indexes are serialized after the hash cache in the shape + of four EWAH bitmaps stored consecutively (see Appendix A for + the serialization format of an EWAH bitmap). + + There is a bitmap for each Git object type, stored in the following + order: + + - Commits + - Trees + - Blobs + - Tags + + In each bitmap, the `n`th bit is set to true if the `n`th object + in the packfile is of that type. + + The obvious consequence is that the OR of all 4 bitmaps will result + in a full set (all bits set), and the AND of all 4 bitmaps will + result in an empty bitmap (no bits set). + + - N entries with compressed bitmaps, one for each indexed commit + + Where `N` is the total amount of entries in this bitmap index. + Each entry contains the following: + + - 4-byte object position (network byte order) + The position **in the index for the packfile** where the + bitmap for this commit is found. + + - 1-byte XOR-offset + The xor offset used to compress this bitmap. For an entry + in position `x`, a XOR offset of `y` means that the actual + bitmap representing this commit is composed by XORing the + bitmap for this entry with the bitmap in entry `x-y` (i.e. + the bitmap `y` entries before this one). + + Note that this compression can be recursive. In order to + XOR this entry with a previous one, the previous entry needs + to be decompressed first, and so on. + + The hard-limit for this offset is 160 (an entry can only be + xor'ed against one of the 160 entries preceding it). This + number is always positive, and hence entries are always xor'ed + with **previous** bitmaps, not bitmaps that will come afterwards + in the index. + + - 1-byte flags for this bitmap + At the moment the only available flag is `0x1`, which hints + that this bitmap can be re-used when rebuilding bitmap indexes + for the repository. + + - The compressed bitmap itself, see Appendix A. + +== Appendix A: Serialization format for an EWAH bitmap + +Ewah bitmaps are serialized in the same protocol as the JAVAEWAH +library, making them backwards compatible with the JGit +implementation: + + - 4-byte number of bits of the resulting UNCOMPRESSED bitmap + + - 4-byte number of words of the COMPRESSED bitmap, when stored + + - N x 8-byte words, as specified by the previous field + + This is the actual content of the compressed bitmap. + + - 4-byte position of the current RLW for the compressed + bitmap + +All words are stored in network byte order for their corresponding +sizes. + +The compressed bitmap is stored in a form of run-length encoding, as +follows. It consists of a concatenation of an arbitrary number of +chunks. Each chunk consists of one or more 64-bit words + + H L_1 L_2 L_3 .... L_M + +H is called RLW (run length word). It consists of (from lower to higher +order bits): + + - 1 bit: the repeated bit B + + - 32 bits: repetition count K (unsigned) + + - 31 bits: literal word count M (unsigned) + +The bitstream represented by the above chunk is then: + + - K repetitions of B + + - The bits stored in `L_1` through `L_M`. Within a word, bits at + lower order come earlier in the stream than those at higher + order. + +The next word after `L_M` (if any) must again be a RLW, for the next +chunk. For efficient appending to the bitstream, the EWAH stores a +pointer to the last RLW in the stream. + + +== Appendix B: Optional Bitmap Sections + +These sections may or may not be present in the `.bitmap` file; their +presence is indicated by the header flags section described above. + +Name-hash cache +--------------- + +If the BITMAP_OPT_HASH_CACHE flag is set, the end of the bitmap contains +a cache of 32-bit values, one per object in the pack. The value at +position `i` is the hash of the pathname at which the `i`th object +(counting in index order) in the pack can be found. This can be fed +into the delta heuristics to compare objects with similar pathnames. + +The hash algorithm used is: + + hash = 0; + while ((c = *name++)) + if (!isspace(c)) + hash = (hash >> 2) + (c << 24); + +Note that this hashing scheme is tied to the BITMAP_OPT_HASH_CACHE flag. +If implementations want to choose a different hashing scheme, they are +free to do so, but MUST allocate a new header flag (because comparing +hashes made under two different schemes would be pointless). diff --git a/Documentation/technical/http-protocol.txt b/Documentation/technical/http-protocol.txt index d21d77d1de..229f845dfa 100644 --- a/Documentation/technical/http-protocol.txt +++ b/Documentation/technical/http-protocol.txt @@ -20,13 +20,13 @@ URL syntax documented by RFC 1738, so they are of the form: http://<host>:<port>/<path>?<searchpart> -Within this documentation the placeholder $GIT_URL will stand for +Within this documentation the placeholder `$GIT_URL` will stand for the http:// repository URL entered by the end-user. -Servers SHOULD handle all requests to locations matching $GIT_URL, as +Servers SHOULD handle all requests to locations matching `$GIT_URL`, as both the "smart" and "dumb" HTTP protocols used by Git operate by appending additional path components onto the end of the user -supplied $GIT_URL string. +supplied `$GIT_URL` string. An example of a dumb client requesting for a loose object: @@ -43,10 +43,10 @@ An example of a request to a submodule: $GIT_URL: http://example.com/git/repo.git/path/submodule.git URL request: http://example.com/git/repo.git/path/submodule.git/info/refs -Clients MUST strip a trailing '/', if present, from the user supplied -$GIT_URL string to prevent empty path tokens ('//') from appearing +Clients MUST strip a trailing `/`, if present, from the user supplied +`$GIT_URL` string to prevent empty path tokens (`//`) from appearing in any URL sent to a server. Compatible clients MUST expand -'$GIT_URL/info/refs' as 'foo/info/refs' and not 'foo//info/refs'. +`$GIT_URL/info/refs` as `foo/info/refs` and not `foo//info/refs`. Authentication @@ -60,7 +60,7 @@ Because Git repositories are accessed by standard path components server administrators MAY use directory based permissions within their HTTP server to control repository access. -Clients SHOULD support Basic authentication as described by RFC 2616. +Clients SHOULD support Basic authentication as described by RFC 2617. Servers SHOULD support Basic authentication by relying upon the HTTP server placed in front of the Git server software. @@ -103,14 +103,14 @@ Except where noted, all standard HTTP behavior SHOULD be assumed by both client and server. This includes (but is not necessarily limited to): -If there is no repository at $GIT_URL, or the resource pointed to by a -location matching $GIT_URL does not exist, the server MUST NOT respond -with '200 OK' response. A server SHOULD respond with -'404 Not Found', '410 Gone', or any other suitable HTTP status code +If there is no repository at `$GIT_URL`, or the resource pointed to by a +location matching `$GIT_URL` does not exist, the server MUST NOT respond +with `200 OK` response. A server SHOULD respond with +`404 Not Found`, `410 Gone`, or any other suitable HTTP status code which does not imply the resource exists as requested. -If there is a repository at $GIT_URL, but access is not currently -permitted, the server MUST respond with the '403 Forbidden' HTTP +If there is a repository at `$GIT_URL`, but access is not currently +permitted, the server MUST respond with the `403 Forbidden` HTTP status code. Servers SHOULD support both HTTP 1.0 and HTTP 1.1. @@ -126,9 +126,9 @@ Servers MAY return ETag and/or Last-Modified headers. Clients MAY revalidate cached entities by including If-Modified-Since and/or If-None-Match request headers. -Servers MAY return '304 Not Modified' if the relevant headers appear +Servers MAY return `304 Not Modified` if the relevant headers appear in the request and the entity has not changed. Clients MUST treat -'304 Not Modified' identical to '200 OK' by reusing the cached entity. +`304 Not Modified` identical to `200 OK` by reusing the cached entity. Clients MAY reuse a cached entity without revalidation if the Cache-Control and/or Expires header permits caching. Clients and @@ -148,7 +148,7 @@ HTTP clients that only support the "dumb" protocol MUST discover references by making a request for the special info/refs file of the repository. -Dumb HTTP clients MUST make a GET request to $GIT_URL/info/refs, +Dumb HTTP clients MUST make a `GET` request to `$GIT_URL/info/refs`, without any search/query parameters. C: GET $GIT_URL/info/refs HTTP/1.0 @@ -161,21 +161,21 @@ without any search/query parameters. S: a3c2e2402b99163d1d59756e5f207ae21cccba4c refs/tags/v1.0^{} The Content-Type of the returned info/refs entity SHOULD be -"text/plain; charset=utf-8", but MAY be any content type. +`text/plain; charset=utf-8`, but MAY be any content type. Clients MUST NOT attempt to validate the returned Content-Type. Dumb servers MUST NOT return a return type starting with -"application/x-git-". +`application/x-git-`. Cache-Control headers MAY be returned to disable caching of the returned entity. When examining the response clients SHOULD only examine the HTTP -status code. Valid responses are '200 OK', or '304 Not Modified'. +status code. Valid responses are `200 OK`, or `304 Not Modified`. The returned content is a UNIX formatted text file describing each ref and its known value. The file SHOULD be sorted by name according to the C locale ordering. The file SHOULD NOT include -the default ref named 'HEAD'. +the default ref named `HEAD`. info_refs = *( ref_record ) ref_record = any_ref / peeled_ref @@ -192,13 +192,14 @@ HTTP clients that support the "smart" protocol (or both the a parameterized request for the info/refs file of the repository. The request MUST contain exactly one query parameter, -'service=$servicename', where $servicename MUST be the service +`service=$servicename`, where `$servicename` MUST be the service name the client wishes to contact to complete the operation. The request MUST NOT contain additional query parameters. C: GET $GIT_URL/info/refs?service=git-upload-pack HTTP/1.0 - dumb server reply: +dumb server reply: + S: 200 OK S: S: 95dcfa3633004da0049d3d0fa03f80589cbcaf31 refs/heads/maint @@ -206,7 +207,8 @@ The request MUST NOT contain additional query parameters. S: 2cb58b79488a98d2721cea644875a8dd0026b115 refs/tags/v1.0 S: a3c2e2402b99163d1d59756e5f207ae21cccba4c refs/tags/v1.0^{} - smart server reply: +smart server reply: + S: 200 OK S: Content-Type: application/x-git-upload-pack-advertisement S: Cache-Control: no-cache @@ -228,7 +230,7 @@ Smart Server Response ^^^^^^^^^^^^^^^^^^^^^ If the server does not recognize the requested service name, or the requested service name has been disabled by the server administrator, -the server MUST respond with the '403 Forbidden' HTTP status code. +the server MUST respond with the `403 Forbidden` HTTP status code. Otherwise, smart servers MUST respond with the smart server reply format for the requested service name. @@ -236,35 +238,35 @@ format for the requested service name. Cache-Control headers SHOULD be used to disable caching of the returned entity. -The Content-Type MUST be 'application/x-$servicename-advertisement'. +The Content-Type MUST be `application/x-$servicename-advertisement`. Clients SHOULD fall back to the dumb protocol if another content type is returned. When falling back to the dumb protocol clients -SHOULD NOT make an additional request to $GIT_URL/info/refs, but +SHOULD NOT make an additional request to `$GIT_URL/info/refs`, but instead SHOULD use the response already in hand. Clients MUST NOT continue if they do not support the dumb protocol. -Clients MUST validate the status code is either '200 OK' or -'304 Not Modified'. +Clients MUST validate the status code is either `200 OK` or +`304 Not Modified`. Clients MUST validate the first five bytes of the response entity -matches the regex "^[0-9a-f]{4}#". If this test fails, clients +matches the regex `^[0-9a-f]{4}#`. If this test fails, clients MUST NOT continue. Clients MUST parse the entire response as a sequence of pkt-line records. -Clients MUST verify the first pkt-line is "# service=$servicename". +Clients MUST verify the first pkt-line is `# service=$servicename`. Servers MUST set $servicename to be the request parameter value. Servers SHOULD include an LF at the end of this line. Clients MUST ignore an LF at the end of the line. -Servers MUST terminate the response with the magic "0000" end +Servers MUST terminate the response with the magic `0000` end pkt-line marker. The returned response is a pkt-line stream describing each ref and its known value. The stream SHOULD be sorted by name according to the C locale ordering. The stream SHOULD include the default ref -named 'HEAD' as the first ref. The stream MUST include capability +named `HEAD` as the first ref. The stream MUST include capability declarations behind a NUL on the first ref. smart_reply = PKT-LINE("# service=$servicename" LF) @@ -286,12 +288,13 @@ declarations behind a NUL on the first ref. peeled_ref = PKT-LINE(obj-id SP name LF) PKT-LINE(obj-id SP name "^{}" LF + Smart Service git-upload-pack ------------------------------ -This service reads from the repository pointed to by $GIT_URL. +This service reads from the repository pointed to by `$GIT_URL`. Clients MUST first perform ref discovery with -'$GIT_URL/info/refs?service=git-upload-pack'. +`$GIT_URL/info/refs?service=git-upload-pack`. C: POST $GIT_URL/git-upload-pack HTTP/1.0 C: Content-Type: application/x-git-upload-pack-request @@ -313,10 +316,10 @@ to prevent caching of the response. Servers SHOULD support all capabilities defined here. -Clients MUST send at least one 'want' command in the request body. -Clients MUST NOT reference an id in a 'want' command which did not +Clients MUST send at least one "want" command in the request body. +Clients MUST NOT reference an id in a "want" command which did not appear in the response obtained through ref discovery unless the -server advertises capability "allow-tip-sha1-in-want". +server advertises capability `allow-tip-sha1-in-want`. compute_request = want_list have_list @@ -332,128 +335,128 @@ server advertises capability "allow-tip-sha1-in-want". have_list = *PKT-LINE("have" SP id LF) TODO: Document this further. -TODO: Don't use uppercase for variable names below. The Negotiation Algorithm ~~~~~~~~~~~~~~~~~~~~~~~~~ The computation to select the minimal pack proceeds as follows -(c = client, s = server): +(C = client, S = server): + +'init step:' + +C: Use ref discovery to obtain the advertised refs. + +C: Place any object seen into set `advertised`. - init step: - (c) Use ref discovery to obtain the advertised refs. - (c) Place any object seen into set ADVERTISED. +C: Build an empty set, `common`, to hold the objects that are later + determined to be on both ends. - (c) Build an empty set, COMMON, to hold the objects that are later - determined to be on both ends. - (c) Build a set, WANT, of the objects from ADVERTISED the client - wants to fetch, based on what it saw during ref discovery. +C: Build a set, `want`, of the objects from `advertised` the client + wants to fetch, based on what it saw during ref discovery. - (c) Start a queue, C_PENDING, ordered by commit time (popping newest - first). Add all client refs. When a commit is popped from - the queue its parents SHOULD be automatically inserted back. - Commits MUST only enter the queue once. +C: Start a queue, `c_pending`, ordered by commit time (popping newest + first). Add all client refs. When a commit is popped from + the queue its parents SHOULD be automatically inserted back. + Commits MUST only enter the queue once. - one compute step: - (c) Send one $GIT_URL/git-upload-pack request: +'one compute step:' - C: 0032want <WANT #1>............................... - C: 0032want <WANT #2>............................... +C: Send one `$GIT_URL/git-upload-pack` request: + + C: 0032want <want #1>............................... + C: 0032want <want #2>............................... .... - C: 0032have <COMMON #1>............................. - C: 0032have <COMMON #2>............................. + C: 0032have <common #1>............................. + C: 0032have <common #2>............................. .... - C: 0032have <HAVE #1>............................... - C: 0032have <HAVE #2>............................... + C: 0032have <have #1>............................... + C: 0032have <have #2>............................... .... C: 0000 - The stream is organized into "commands", with each command - appearing by itself in a pkt-line. Within a command line - the text leading up to the first space is the command name, - and the remainder of the line to the first LF is the value. - Command lines are terminated with an LF as the last byte of - the pkt-line value. +The stream is organized into "commands", with each command +appearing by itself in a pkt-line. Within a command line, +the text leading up to the first space is the command name, +and the remainder of the line to the first LF is the value. +Command lines are terminated with an LF as the last byte of +the pkt-line value. - Commands MUST appear in the following order, if they appear - at all in the request stream: +Commands MUST appear in the following order, if they appear +at all in the request stream: - * want - * have +* "want" +* "have" - The stream is terminated by a pkt-line flush ("0000"). +The stream is terminated by a pkt-line flush (`0000`). - A single "want" or "have" command MUST have one hex formatted - SHA-1 as its value. Multiple SHA-1s MUST be sent by sending - multiple commands. +A single "want" or "have" command MUST have one hex formatted +SHA-1 as its value. Multiple SHA-1s MUST be sent by sending +multiple commands. - The HAVE list is created by popping the first 32 commits - from C_PENDING. Less can be supplied if C_PENDING empties. +The `have` list is created by popping the first 32 commits +from `c_pending`. Less can be supplied if `c_pending` empties. - If the client has sent 256 HAVE commits and has not yet - received one of those back from S_COMMON, or the client has - emptied C_PENDING it SHOULD include a "done" command to let - the server know it won't proceed: +If the client has sent 256 "have" commits and has not yet +received one of those back from `s_common`, or the client has +emptied `c_pending` it SHOULD include a "done" command to let +the server know it won't proceed: C: 0009done - (s) Parse the git-upload-pack request: - - Verify all objects in WANT are directly reachable from refs. - - The server MAY walk backwards through history or through - the reflog to permit slightly stale requests. +S: Parse the git-upload-pack request: - If no WANT objects are received, send an error: +Verify all objects in `want` are directly reachable from refs. -TODO: Define error if no want lines are requested. +The server MAY walk backwards through history or through +the reflog to permit slightly stale requests. - If any WANT object is not reachable, send an error: +If no "want" objects are received, send an error: +TODO: Define error if no "want" lines are requested. -TODO: Define error if an invalid want is requested. +If any "want" object is not reachable, send an error: +TODO: Define error if an invalid "want" is requested. - Create an empty list, S_COMMON. +Create an empty list, `s_common`. - If 'have' was sent: +If "have" was sent: - Loop through the objects in the order supplied by the client. - For each object, if the server has the object reachable from - a ref, add it to S_COMMON. If a commit is added to S_COMMON, - do not add any ancestors, even if they also appear in HAVE. +Loop through the objects in the order supplied by the client. - (s) Send the git-upload-pack response: +For each object, if the server has the object reachable from +a ref, add it to `s_common`. If a commit is added to `s_common`, +do not add any ancestors, even if they also appear in `have`. - If the server has found a closed set of objects to pack or the - request ends with "done", it replies with the pack. +S: Send the git-upload-pack response: +If the server has found a closed set of objects to pack or the +request ends with "done", it replies with the pack. TODO: Document the pack based response - S: PACK... - The returned stream is the side-band-64k protocol supported - by the git-upload-pack service, and the pack is embedded into - stream 1. Progress messages from the server side MAY appear - in stream 2. + S: PACK... - Here a "closed set of objects" is defined to have at least - one path from every WANT to at least one COMMON object. +The returned stream is the side-band-64k protocol supported +by the git-upload-pack service, and the pack is embedded into +stream 1. Progress messages from the server side MAY appear +in stream 2. - If the server needs more information, it replies with a - status continue response: +Here a "closed set of objects" is defined to have at least +one path from every "want" to at least one "common" object. +If the server needs more information, it replies with a +status continue response: TODO: Document the non-pack response - (c) Parse the upload-pack response: - -TODO: Document parsing response +C: Parse the upload-pack response: + TODO: Document parsing response - Do another compute step. +'Do another compute step.' Smart Service git-receive-pack ------------------------------ -This service reads from the repository pointed to by $GIT_URL. +This service reads from the repository pointed to by `$GIT_URL`. Clients MUST first perform ref discovery with -'$GIT_URL/info/refs?service=git-receive-pack'. +`$GIT_URL/info/refs?service=git-receive-pack`. C: POST $GIT_URL/git-receive-pack HTTP/1.0 C: Content-Type: application/x-git-receive-pack-request @@ -497,7 +500,7 @@ TODO: Document this further. References ---------- -link:http://www.ietf.org/rfc/rfc1738.txt[RFC 1738: Uniform Resource Locators (URL)] -link:http://www.ietf.org/rfc/rfc2616.txt[RFC 2616: Hypertext Transfer Protocol -- HTTP/1.1] +http://www.ietf.org/rfc/rfc1738.txt[RFC 1738: Uniform Resource Locators (URL)] +http://www.ietf.org/rfc/rfc2616.txt[RFC 2616: Hypertext Transfer Protocol -- HTTP/1.1] link:technical/pack-protocol.html link:technical/protocol-capabilities.html diff --git a/Documentation/technical/index-format.txt b/Documentation/technical/index-format.txt index f352a9b22e..fe6f31667d 100644 --- a/Documentation/technical/index-format.txt +++ b/Documentation/technical/index-format.txt @@ -129,6 +129,9 @@ Git index format (Version 4) In version 4, the padding after the pathname does not exist. + Interpretation of index entries in split index mode is completely + different. See below for details. + == Extensions === Cached tree @@ -198,3 +201,35 @@ Git index format - At most three 160-bit object names of the entry in stages from 1 to 3 (nothing is written for a missing stage). +=== Split index + + In split index mode, the majority of index entries could be stored + in a separate file. This extension records the changes to be made on + top of that to produce the final index. + + The signature for this extension is { 'l', 'i, 'n', 'k' }. + + The extension consists of: + + - 160-bit SHA-1 of the shared index file. The shared index file path + is $GIT_DIR/sharedindex.<SHA-1>. If all 160 bits are zero, the + index does not require a shared index file. + + - An ewah-encoded delete bitmap, each bit represents an entry in the + shared index. If a bit is set, its corresponding entry in the + shared index will be removed from the final index. Note, because + a delete operation changes index entry positions, but we do need + original positions in replace phase, it's best to just mark + entries for removal, then do a mass deletion after replacement. + + - An ewah-encoded replace bitmap, each bit represents an entry in + the shared index. If a bit is set, its corresponding entry in the + shared index will be replaced with an entry in this index + file. All replaced entries are stored in sorted order in this + index. The first "1" bit in the replace bitmap corresponds to the + first index entry, the second "1" bit to the second entry and so + on. Replaced entries may have empty path names to save space. + + The remaining index entries after replaced ones will be added to the + final index. These added entries are also sorted by entry namme then + stage. diff --git a/Documentation/technical/pack-protocol.txt b/Documentation/technical/pack-protocol.txt index b898e97988..462e20645f 100644 --- a/Documentation/technical/pack-protocol.txt +++ b/Documentation/technical/pack-protocol.txt @@ -161,6 +161,7 @@ MUST peel the ref if it's an annotated tag. ---- advertised-refs = (no-refs / list-of-refs) + *shallow flush-pkt no-refs = PKT-LINE(zero-id SP "capabilities^{}" @@ -174,6 +175,8 @@ MUST peel the ref if it's an annotated tag. other-tip = obj-id SP refname LF other-peeled = obj-id SP refname "^{}" LF + shallow = PKT-LINE("shallow" SP obj-id) + capability-list = capability *(SP capability) capability = 1*(LC_ALPHA / DIGIT / "-" / "_") LC_ALPHA = %x61-7A @@ -209,9 +212,9 @@ out of what the server said it could do with the first 'want' line. want-list = first-want *additional-want - shallow-line = PKT_LINE("shallow" SP obj-id) + shallow-line = PKT-LINE("shallow" SP obj-id) - depth-request = PKT_LINE("deepen" SP depth) + depth-request = PKT-LINE("deepen" SP depth) first-want = PKT-LINE("want" SP obj-id SP capability-list LF) additional-want = PKT-LINE("want" SP obj-id LF) @@ -234,10 +237,10 @@ The client now sends the maximum commit history depth it wants for this transaction, which is the number of commits it wants from the tip of the history, if any, as a 'deepen' line. A depth of 0 is the same as not making a depth request. The client does not want to receive -any commits beyond this depth, nor objects needed only to complete -those commits. Commits whose parents are not received as a result are -defined as shallow and marked as such in the server. This information -is sent back to the client in the next step. +any commits beyond this depth, nor does it want objects needed only to +complete those commits. Commits whose parents are not received as a +result are defined as shallow and marked as such in the server. This +information is sent back to the client in the next step. Once all the 'want's and 'shallow's (and optional 'deepen') are transferred, clients MUST send a flush-pkt, to tell the server side @@ -335,7 +338,8 @@ during a prior round. This helps to ensure that at least one common ancestor is found before we give up entirely. Once the 'done' line is read from the client, the server will either -send a final 'ACK obj-id' or it will send a 'NAK'. The server only sends +send a final 'ACK obj-id' or it will send a 'NAK'. 'obj-id' is the object +name of the last commit determined to be common. The server only sends ACK after 'done' if there is at least one common base and multi_ack or multi_ack_detailed is enabled. The server always sends NAK after 'done' if there is no common base found. @@ -461,7 +465,9 @@ contain all the objects that the server will need to complete the new references. ---- - update-request = command-list [pack-file] + update-request = *shallow ( command-list | push-cert ) [pack-file] + + shallow = PKT-LINE("shallow" SP obj-id LF) command-list = PKT-LINE(command NUL capability-list LF) *PKT-LINE(command LF) @@ -475,12 +481,27 @@ references. old-id = obj-id new-id = obj-id + push-cert = PKT-LINE("push-cert" NUL capability-list LF) + PKT-LINE("certificate version 0.1" LF) + PKT-LINE("pusher" SP ident LF) + PKT-LINE("pushee" SP url LF) + PKT-LINE("nonce" SP nonce LF) + PKT-LINE(LF) + *PKT-LINE(command LF) + *PKT-LINE(gpg-signature-lines LF) + PKT-LINE("push-cert-end" LF) + pack-file = "PACK" 28*(OCTET) ---- If the receiving end does not support delete-refs, the sending end MUST NOT ask for delete command. +If the receiving end does not support push-cert, the sending end +MUST NOT send a push-cert command. When a push-cert command is +sent, command-list MUST NOT be sent; the commands recorded in the +push certificate is used instead. + The pack-file MUST NOT be sent if the only command used is 'delete'. A pack-file MUST be sent if either create or update command is used, @@ -495,6 +516,34 @@ was being processed (the obj-id is still the same as the old-id), and it will run any update hooks to make sure that the update is acceptable. If all of that is fine, the server will then update the references. +Push Certificate +---------------- + +A push certificate begins with a set of header lines. After the +header and an empty line, the protocol commands follow, one per +line. + +Currently, the following header fields are defined: + +`pusher` ident:: + Identify the GPG key in "Human Readable Name <email@address>" + format. + +`pushee` url:: + The repository URL (anonymized, if the URL contains + authentication material) the user who ran `git push` + intended to push into. + +`nonce` nonce:: + The 'nonce' string the receiving repository asked the + pushing user to include in the certificate, to prevent + replay attacks. + +The GPG signature lines are a detached signature for the contents +recorded in the push certificate before the signature block begins. +The detached signature is used to certify that the commands were +given by the pusher, who must be the signer. + Report Status ------------- diff --git a/Documentation/technical/protocol-capabilities.txt b/Documentation/technical/protocol-capabilities.txt index fd8ffa5df3..0c92deebcc 100644 --- a/Documentation/technical/protocol-capabilities.txt +++ b/Documentation/technical/protocol-capabilities.txt @@ -18,8 +18,8 @@ was sent. Server MUST NOT ignore capabilities that client requested and server advertised. As a consequence of these rules, server MUST NOT advertise capabilities it does not understand. -The 'report-status', 'delete-refs', and 'quiet' capabilities are sent and -recognized by the receive-pack (push to server) process. +The 'report-status', 'delete-refs', 'quiet', and 'push-cert' capabilities +are sent and recognized by the receive-pack (push to server) process. The 'ofs-delta' and 'side-band-64k' capabilities are sent and recognized by both upload-pack and receive-pack protocols. The 'agent' capability @@ -69,17 +69,50 @@ ends. Without multi_ack the client would have sent that c-b-a chain anyway, interleaved with S-R-Q. +multi_ack_detailed +------------------ +This is an extension of multi_ack that permits client to better +understand the server's in-memory state. See pack-protocol.txt, +section "Packfile Negotiation" for more information. + +no-done +------- +This capability should only be used with the smart HTTP protocol. If +multi_ack_detailed and no-done are both present, then the sender is +free to immediately send a pack following its first "ACK obj-id ready" +message. + +Without no-done in the smart HTTP protocol, the server session would +end and the client has to make another trip to send "done" before +the server can send the pack. no-done removes the last round and +thus slightly reduces latency. + thin-pack --------- -This capability means that the server can send a 'thin' pack, a pack -which does not contain base objects; if those base objects are available -on client side. Client requests 'thin-pack' capability when it -understands how to "thicken" it by adding required delta bases making -it self-contained. +A thin pack is one with deltas which reference base objects not +contained within the pack (but are known to exist at the receiving +end). This can reduce the network traffic significantly, but it +requires the receiving end to know how to "thicken" these packs by +adding the missing bases to the pack. -Client MUST NOT request 'thin-pack' capability if it cannot turn a thin -pack into a self-contained pack. +The upload-pack server advertises 'thin-pack' when it can generate +and send a thin pack. A client requests the 'thin-pack' capability +when it understands how to "thicken" it, notifying the server that +it can receive such a pack. A client MUST NOT request the +'thin-pack' capability if it cannot turn a thin pack into a +self-contained pack. + +Receive-pack, on the other hand, is assumed by default to be able to +handle thin packs, but can ask the client not to use the feature by +advertising the 'no-thin' capability. A client MUST NOT send a thin +pack if the server advertises the 'no-thin' capability. + +The reasons for this asymmetry are historical. The receive-pack +program did not exist until after the invention of thin packs, so +historically the reference implementation of receive-pack always +understood thin packs. Adding 'no-thin' later allowed receive-pack +to disable the feature in a backwards-compatible manner. side-band, side-band-64k @@ -217,3 +250,12 @@ allow-tip-sha1-in-want If the upload-pack server advertises this capability, fetch-pack may send "want" lines with SHA-1s that exist at the server but are not advertised by upload-pack. + +push-cert=<nonce> +----------------- + +The receive-pack server that advertises this capability is willing +to accept a signed push certificate, and asks the <nonce> to be +included in the push certificate. A send-pack client MUST NOT +send a push-cert packet unless the receive-pack server advertises +this capability. diff --git a/Documentation/technical/protocol-common.txt b/Documentation/technical/protocol-common.txt index fb7ff084f8..889985f707 100644 --- a/Documentation/technical/protocol-common.txt +++ b/Documentation/technical/protocol-common.txt @@ -39,7 +39,7 @@ More specifically, they: caret `^`, colon `:`, question-mark `?`, asterisk `*`, or open bracket `[` anywhere. -. They cannot end with a slash `/` nor a dot `.`. +. They cannot end with a slash `/` or a dot `.`. . They cannot end with the sequence `.lock`. |