diff options
Diffstat (limited to 'Documentation/technical')
| -rw-r--r-- | Documentation/technical/api-builtin.txt | 2 | ||||
| -rw-r--r-- | Documentation/technical/api-directory-listing.txt | 3 | ||||
| -rw-r--r-- | Documentation/technical/api-hash.txt | 50 | ||||
| -rw-r--r-- | Documentation/technical/api-history-graph.txt | 5 | ||||
| -rw-r--r-- | Documentation/technical/api-merge.txt | 104 | ||||
| -rw-r--r-- | Documentation/technical/api-parse-options.txt | 78 | ||||
| -rw-r--r-- | Documentation/technical/api-remote.txt | 4 | ||||
| -rw-r--r-- | Documentation/technical/api-run-command.txt | 105 | ||||
| -rw-r--r-- | Documentation/technical/api-sigchain.txt | 41 | ||||
| -rw-r--r-- | Documentation/technical/api-strbuf.txt | 41 | ||||
| -rw-r--r-- | Documentation/technical/api-string-list.txt | 10 | ||||
| -rw-r--r-- | Documentation/technical/api-tree-walking.txt | 149 | ||||
| -rw-r--r-- | Documentation/technical/index-format.txt | 185 | ||||
| -rw-r--r-- | Documentation/technical/pack-protocol.txt | 535 | ||||
| -rw-r--r-- | Documentation/technical/protocol-capabilities.txt | 187 | ||||
| -rw-r--r-- | Documentation/technical/protocol-common.txt | 96 | ||||
| -rw-r--r-- | Documentation/technical/racy-git.txt | 12 |
17 files changed, 1512 insertions, 95 deletions
diff --git a/Documentation/technical/api-builtin.txt b/Documentation/technical/api-builtin.txt index 7ede1e64e5..5cb2b0590a 100644 --- a/Documentation/technical/api-builtin.txt +++ b/Documentation/technical/api-builtin.txt @@ -37,7 +37,7 @@ where options is the bitwise-or of: Make sure there is a work tree, i.e. the command cannot act on bare repositories. - This makes only sense when `RUN_SETUP` is also set. + This only makes sense when `RUN_SETUP` is also set. . Add `builtin-foo.o` to `BUILTIN_OBJS` in `Makefile`. diff --git a/Documentation/technical/api-directory-listing.txt b/Documentation/technical/api-directory-listing.txt index 5bbd18f020..add6f435b5 100644 --- a/Documentation/technical/api-directory-listing.txt +++ b/Documentation/technical/api-directory-listing.txt @@ -58,6 +58,9 @@ The result of the enumeration is left in these fields:: Calling sequence ---------------- +Note: index may be looked at for .gitignore files that are CE_SKIP_WORKTREE +marked. If you to exclude files, make sure you have loaded index first. + * Prepare `struct dir_struct dir` and clear it with `memset(&dir, 0, sizeof(dir))`. diff --git a/Documentation/technical/api-hash.txt b/Documentation/technical/api-hash.txt index c784d3edcb..e5061e0677 100644 --- a/Documentation/technical/api-hash.txt +++ b/Documentation/technical/api-hash.txt @@ -1,6 +1,52 @@ hash API ======== -Talk about <hash.h> +The hash API is a collection of simple hash table functions. Users are expected +to implement their own hashing. -(Linus) +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-history-graph.txt b/Documentation/technical/api-history-graph.txt index d66e61b1ec..d6fc90ac7e 100644 --- a/Documentation/technical/api-history-graph.txt +++ b/Documentation/technical/api-history-graph.txt @@ -11,9 +11,6 @@ Core functions: * `graph_init()` creates a new `struct git_graph` -* `graph_release()` destroys a `struct git_graph`, and frees the memory - associated with it. - * `graph_update()` moves the graph to a new commit. * `graph_next_line()` outputs the next line of the graph into a strbuf. It @@ -134,8 +131,6 @@ while ((commit = get_revision(opts)) != NULL) { putchar(opts->diffopt.line_termination); } } - -graph_release(graph); ------------ Sample output diff --git a/Documentation/technical/api-merge.txt b/Documentation/technical/api-merge.txt new file mode 100644 index 0000000000..9dc1bed768 --- /dev/null +++ b/Documentation/technical/api-merge.txt @@ -0,0 +1,104 @@ +merge API +========= + +The merge API helps a program to reconcile two competing sets of +improvements to some files (e.g., unregistered changes from the work +tree versus changes involved in switching to a new branch), reporting +conflicts if found. The library called through this API is +responsible for a few things. + + * determining which trees to merge (recursive ancestor consolidation); + + * lining up corresponding files in the trees to be merged (rename + detection, subtree shifting), reporting edge cases like add/add + and rename/rename conflicts to the user; + + * performing a three-way merge of corresponding files, taking + path-specific merge drivers (specified in `.gitattributes`) + into account. + +Data structures +--------------- + +* `mmbuffer_t`, `mmfile_t` + +These store data usable for use by the xdiff backend, for writing and +for reading, respectively. See `xdiff/xdiff.h` for the definitions +and `diff.c` for examples. + +* `struct ll_merge_options` + +This describes the set of options the calling program wants to affect +the operation of a low-level (single file) merge. Some options: + +`virtual_ancestor`:: + Behave as though this were part of a merge between common + ancestors in a recursive merge. + If a helper program is specified by the + `[merge "<driver>"] recursive` configuration, it will + be used (see linkgit:gitattributes[5]). + +`variant`:: + Resolve local conflicts automatically in favor + of one side or the other (as in 'git merge-file' + `--ours`/`--theirs`/`--union`). Can be `0`, + `XDL_MERGE_FAVOR_OURS`, `XDL_MERGE_FAVOR_THEIRS`, or + `XDL_MERGE_FAVOR_UNION`. + +`renormalize`:: + Resmudge and clean the "base", "theirs" and "ours" files + before merging. Use this when the merge is likely to have + overlapped with a change in smudge/clean or end-of-line + normalization rules. + +Low-level (single file) merge +----------------------------- + +`ll_merge`:: + + Perform a three-way single-file merge in core. This is + a thin wrapper around `xdl_merge` that takes the path and + any merge backend specified in `.gitattributes` or + `.git/info/attributes` into account. Returns 0 for a + clean merge. + +Calling sequence: + +* Prepare a `struct ll_merge_options` to record options. + If you have no special requests, skip this and pass `NULL` + as the `opts` parameter to use the default options. + +* Allocate an mmbuffer_t variable for the result. + +* Allocate and fill variables with the file's original content + and two modified versions (using `read_mmfile`, for example). + +* Call `ll_merge()`. + +* Read the merged content from `result_buf.ptr` and `result_buf.size`. + +* Release buffers when finished. A simple + `free(ancestor.ptr); free(ours.ptr); free(theirs.ptr); + free(result_buf.ptr);` will do. + +If the modifications do not merge cleanly, `ll_merge` will return a +nonzero value and `result_buf` will generally include a description of +the conflict bracketed by markers such as the traditional `<<<<<<<` +and `>>>>>>>`. + +The `ancestor_label`, `our_label`, and `their_label` parameters are +used to label the different sides of a conflict if the merge driver +supports this. + +Everything else +--------------- + +Talk about <merge-recursive.h> and merge_file(): + + - merge_trees() to merge with rename detection + - merge_recursive() for ancestor consolidation + - try_merge_command() for other strategies + - conflict format + - merge options + +(Daniel, Miklos, Stephan, JC) diff --git a/Documentation/technical/api-parse-options.txt b/Documentation/technical/api-parse-options.txt index 539863b1f9..f6a4a361bd 100644 --- a/Documentation/technical/api-parse-options.txt +++ b/Documentation/technical/api-parse-options.txt @@ -60,12 +60,18 @@ Steps to parse options . in `cmd_foo(int argc, const char **argv, const char *prefix)` call - argc = parse_options(argc, argv, builtin_foo_options, builtin_foo_usage, flags); + argc = parse_options(argc, argv, prefix, builtin_foo_options, builtin_foo_usage, flags); + `parse_options()` will filter out the processed options of `argv[]` and leave the non-option arguments in `argv[]`. `argc` is updated appropriately because of the assignment. + +You can also pass NULL instead of a usage array as the fifth parameter of +parse_options(), to avoid displaying a help screen with usage info and +option list. This should only be done if necessary, e.g. to implement +a limited parser for only a subset of the options that needs to be run +before the full parser, which in turn shows the full help message. ++ Flags are the bitwise-or of: `PARSE_OPT_KEEP_DASHDASH`:: @@ -77,6 +83,28 @@ Flags are the bitwise-or of: Using this flag, processing is stopped at the first non-option argument. +`PARSE_OPT_KEEP_ARGV0`:: + Keep the first argument, which contains the program name. It's + removed from argv[] by default. + +`PARSE_OPT_KEEP_UNKNOWN`:: + Keep unknown arguments instead of erroring out. This doesn't + work for all combinations of arguments as users might expect + it to do. E.g. if the first argument in `--unknown --known` + takes a value (which we can't know), the second one is + mistakenly interpreted as a known option. Similarly, if + `PARSE_OPT_STOP_AT_NON_OPTION` is set, the second argument in + `--unknown value` will be mistakenly interpreted as a + non-option, not as a value belonging to the unknown option, + the parser early. That's why parse_options() errors out if + both options are set. + +`PARSE_OPT_NO_INTERNAL_HELP`:: + By default, parse_options() handles `-h`, `--help` and + `--help-all` internally, by showing a help screen. This option + turns it off and allows one to add custom handlers for these + options, or to just leave them unknown. + Data Structure -------------- @@ -87,13 +115,19 @@ There are some macros to easily define options: `OPT__ABBREV(&int_var)`:: Add `\--abbrev[=<n>]`. -`OPT__DRY_RUN(&int_var)`:: +`OPT__COLOR(&int_var, description)`:: + Add `\--color[=<when>]` and `--no-color`. + +`OPT__DRY_RUN(&int_var, description)`:: Add `-n, \--dry-run`. -`OPT__QUIET(&int_var)`:: +`OPT__FORCE(&int_var, description)`:: + Add `-f, \--force`. + +`OPT__QUIET(&int_var, description)`:: Add `-q, \--quiet`. -`OPT__VERBOSE(&int_var)`:: +`OPT__VERBOSE(&int_var, description)`:: Add `-v, \--verbose`. `OPT_GROUP(description)`:: @@ -109,6 +143,10 @@ There are some macros to easily define options: Introduce a boolean option. If used, `int_var` is bitwise-ored with `mask`. +`OPT_NEGBIT(short, long, &int_var, description, mask)`:: + Introduce a boolean option. + If used, `int_var` is bitwise-anded with the inverted `mask`. + `OPT_SET_INT(short, long, &int_var, description, integer)`:: Introduce a boolean option. If used, set `int_var` to `integer`. @@ -135,16 +173,38 @@ There are some macros to easily define options: and the result will be put into `var`. See 'Option Callbacks' below for a more elaborate description. +`OPT_FILENAME(short, long, &var, description)`:: + Introduce an option with a filename argument. + The filename will be prefixed by passing the filename along with + the prefix argument of `parse_options()` to `prefix_filename()`. + `OPT_ARGUMENT(long, description)`:: Introduce a long-option argument that will be kept in `argv[]`. +`OPT_NUMBER_CALLBACK(&var, description, func_ptr)`:: + Recognize numerical options like -123 and feed the integer as + if it was an argument to the function given by `func_ptr`. + The result will be put into `var`. There can be only one such + option definition. It cannot be negated and it takes no + arguments. Short options that happen to be digits take + precedence over it. + +`OPT_COLOR_FLAG(short, long, &int_var, description)`:: + Introduce an option that takes an optional argument that can + have one of three values: "always", "never", or "auto". If the + argument is not given, it defaults to "always". The `--no-` form + works like `--long=never`; it cannot take an argument. If + "always", set `int_var` to 1; if "never", set `int_var` to 0; if + "auto", set `int_var` to 1 if stdout is a tty or a pager, + 0 otherwise. + The last element of the array must be `OPT_END()`. If not stated otherwise, interpret the arguments as follows: * `short` is a character for the short option - (e.g. `\'e\'` for `-e`, use `0` to omit), + (e.g. `{apostrophe}e{apostrophe}` for `-e`, use `0` to omit), * `long` is a string for the long option (e.g. `"example"` for `\--example`, use `NULL` to omit), @@ -170,11 +230,11 @@ The function must be defined in this form: The callback mechanism is as follows: -* Inside `funct`, the only interesting member of the structure - given by `opt` is the void pointer `opt->value`. - `\*opt->value` will be the value that is saved into `var`, if you +* Inside `func`, the only interesting member of the structure + given by `opt` is the void pointer `opt\->value`. + `\*opt\->value` will be the value that is saved into `var`, if you use `OPT_CALLBACK()`. - For example, do `*(unsigned long *)opt->value = 42;` to get 42 + For example, do `*(unsigned long *)opt\->value = 42;` to get 42 into an `unsigned long` variable. * Return value `0` indicates success and non-zero return diff --git a/Documentation/technical/api-remote.txt b/Documentation/technical/api-remote.txt index 073b22bd83..c54b17db69 100644 --- a/Documentation/technical/api-remote.txt +++ b/Documentation/technical/api-remote.txt @@ -18,6 +18,10 @@ struct remote An array of all of the url_nr URLs configured for the remote +`pushurl`:: + + An array of all of the pushurl_nr push URLs configured for the remote + `push`:: An array of refspecs configured for pushing, with diff --git a/Documentation/technical/api-run-command.txt b/Documentation/technical/api-run-command.txt index 75aa5d4923..f18b4f4817 100644 --- a/Documentation/technical/api-run-command.txt +++ b/Documentation/technical/api-run-command.txt @@ -30,28 +30,63 @@ Functions start_command() followed by finish_command(). Takes a pointer to a `struct child_process` that specifies the details. -`run_command_v_opt`, `run_command_v_opt_cd`, `run_command_v_opt_cd_env`:: +`run_command_v_opt`, `run_command_v_opt_cd_env`:: Convenience functions that encapsulate a sequence of start_command() followed by finish_command(). The argument argv specifies the program and its arguments. The argument opt is zero - or more of the flags `RUN_COMMAND_NO_STDIN`, `RUN_GIT_CMD`, or - `RUN_COMMAND_STDOUT_TO_STDERR` that correspond to the members - .no_stdin, .git_cmd, .stdout_to_stderr of `struct child_process`. + or more of the flags `RUN_COMMAND_NO_STDIN`, `RUN_GIT_CMD`, + `RUN_COMMAND_STDOUT_TO_STDERR`, or `RUN_SILENT_EXEC_FAILURE` + that correspond to the members .no_stdin, .git_cmd, + .stdout_to_stderr, .silent_exec_failure of `struct child_process`. The argument dir corresponds the member .dir. The argument env corresponds to the member .env. +The functions above do the following: + +. If a system call failed, errno is set and -1 is returned. A diagnostic + is printed. + +. If the program was not found, then -1 is returned and errno is set to + ENOENT; a diagnostic is printed only if .silent_exec_failure is 0. + +. Otherwise, the program is run. If it terminates regularly, its exit + code is returned. No diagnostic is printed, even if the exit code is + non-zero. + +. If the program terminated due to a signal, then the return value is the + signal number - 128, ie. it is negative and so indicates an unusual + condition; a diagnostic is printed. This return value can be passed to + exit(2), which will report the same code to the parent process that a + POSIX shell's $? would report for a program that died from the signal. + + `start_async`:: Run a function asynchronously. Takes a pointer to a `struct - async` that specifies the details and returns a pipe FD - from which the caller reads. See below for details. + async` that specifies the details and returns a set of pipe FDs + for communication with the function. See below for details. `finish_async`:: Wait for the completion of an asynchronous function that was started with start_async(). +`run_hook`:: + + Run a hook. + The first argument is a pathname to an index file, or NULL + if the hook uses the default index file or no index is needed. + The second argument is the name of the hook. + The further arguments correspond to the hook arguments. + The last argument has to be NULL to terminate the arguments list. + If the hook does not exist or is not executable, the return + value will be zero. + If it is executable, the hook will be executed and the exit + status of the hook is returned. + On execution, .stdout_to_stderr and .no_stdin will be set. + (See below.) + Data structures --------------- @@ -100,7 +135,7 @@ stderr as follows: .in: The FD must be readable; it becomes child's stdin. .out: The FD must be writable; it becomes child's stdout. - .err > 0 is not supported. + .err: The FD must be writable; it becomes child's stderr. The specified FD is closed by start_command(), even if it fails to run the sub-process! @@ -128,6 +163,11 @@ string pointers (NULL terminated) in .env: To specify a new initial working directory for the sub-process, specify it in the .dir member. +If the program cannot be found, the functions return -1 and set +errno to ENOENT. Normally, an error message is printed, but if +.silent_exec_failure is set to 1, no message is printed for this +special error condition. + * `struct async` @@ -140,17 +180,47 @@ The caller: struct async variable; 2. initializes .proc and .data; 3. calls start_async(); -4. processes the data by reading from the fd in .out; -5. closes .out; +4. processes communicates with proc through .in and .out; +5. closes .in and .out; 6. calls finish_async(). +The members .in, .out are used to provide a set of fd's for +communication between the caller and the callee as follows: + +. Specify 0 to have no file descriptor passed. The callee will + receive -1 in the corresponding argument. + +. Specify < 0 to have a pipe allocated; start_async() replaces + with the pipe FD in the following way: + + .in: Returns the writable pipe end into which the caller + writes; the readable end of the pipe becomes the function's + in argument. + + .out: Returns the readable pipe end from which the caller + reads; the writable end of the pipe becomes the function's + out argument. + + The caller of start_async() must close the returned FDs after it + has completed reading from/writing from them. + +. Specify a file descriptor > 0 to be used by the function: + + .in: The FD must be readable; it becomes the function's in. + .out: The FD must be writable; it becomes the function's out. + + The specified FD is closed by start_async(), even if it fails to + run the function. + The function pointer in .proc has the following signature: - int proc(int fd, void *data); + int proc(int in, int out, void *data); -. fd specifies a writable file descriptor to which the function must - write the data that it produces. The function *must* close this - descriptor before it returns. +. in, out specifies a set of file descriptors to which the function + must read/write the data that it needs/produces. The function + *must* close these descriptors before it returns. A descriptor + may be -1 if the caller did not configure a descriptor for that + direction. . data is the value that the caller has specified in the .data member of struct async. @@ -161,12 +231,13 @@ The function pointer in .proc has the following signature: There are serious restrictions on what the asynchronous function can do -because this facility is implemented by a pipe to a forked process on -UNIX, but by a thread in the same address space on Windows: +because this facility is implemented by a thread in the same address +space on most platforms (when pthreads is available), but by a pipe to +a forked process otherwise: . It cannot change the program's state (global variables, environment, - etc.) in a way that the caller notices; in other words, .out is the - only communication channel to the caller. + etc.) in a way that the caller notices; in other words, .in and .out + are the only communication channels to the caller. . It must not change the program's state that the caller of the facility also uses. diff --git a/Documentation/technical/api-sigchain.txt b/Documentation/technical/api-sigchain.txt new file mode 100644 index 0000000000..9e1189ef01 --- /dev/null +++ b/Documentation/technical/api-sigchain.txt @@ -0,0 +1,41 @@ +sigchain API +============ + +Code often wants to set a signal handler to clean up temporary files or +other work-in-progress when we die unexpectedly. For multiple pieces of +code to do this without conflicting, each piece of code must remember +the old value of the handler and restore it either when: + + 1. The work-in-progress is finished, and the handler is no longer + necessary. The handler should revert to the original behavior + (either another handler, SIG_DFL, or SIG_IGN). + + 2. The signal is received. We should then do our cleanup, then chain + to the next handler (or die if it is SIG_DFL). + +Sigchain is a tiny library for keeping a stack of handlers. Your handler +and installation code should look something like: + +------------------------------------------ + void clean_foo_on_signal(int sig) + { + clean_foo(); + sigchain_pop(sig); + raise(sig); + } + + void other_func() + { + sigchain_push_common(clean_foo_on_signal); + mess_up_foo(); + clean_foo(); + } +------------------------------------------ + +Handlers are given the typedef of sigchain_fun. This is the same type +that is given to signal() or sigaction(). It is perfectly reasonable to +push SIG_DFL or SIG_IGN onto the stack. + +You can sigchain_push and sigchain_pop individual signals. For +convenience, sigchain_push_common will push the handler onto the stack +for many common signals. diff --git a/Documentation/technical/api-strbuf.txt b/Documentation/technical/api-strbuf.txt index 4242dc0142..afe2759951 100644 --- a/Documentation/technical/api-strbuf.txt +++ b/Documentation/technical/api-strbuf.txt @@ -12,7 +12,7 @@ strbuf API actually relies on the string being free of NULs. strbufs has some invariants that are very important to keep in mind: -. The `buf` member is never NULL, so you it can be used in any usual C +. 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 `strbuf_init()` or by `= STRBUF_INIT` before the invariants, though. + @@ -55,7 +55,7 @@ Data structures * `struct strbuf` -This is string buffer structure. The `len` member can be used to +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. @@ -133,8 +133,10 @@ Functions * Adding data to the buffer -NOTE: All of these functions in this section will grow the buffer as - necessary. +NOTE: All of the functions in this section will grow the buffer as necessary. +If they fail for some reason other than memory shortage and the buffer hadn't +been allocated before (i.e. the `struct strbuf` was set to `STRBUF_INIT`), +then they will free() it. `strbuf_addch`:: @@ -197,6 +199,10 @@ character if the letter `n` appears after a `%`. The function returns the length of the placeholder recognized and `strbuf_expand()` skips over it. + +The format `%%` is automatically expanded to a single `%` as a quoting +mechanism; callers do not need to handle the `%` placeholder themselves, +and the callback function will not be invoked for this placeholder. ++ All other characters (non-percent and not skipped ones) are copied verbatim to the strbuf. If the callback returned zero, meaning that the placeholder is unknown, then the percent sign is copied, too. @@ -205,6 +211,20 @@ In order to facilitate caching and to make it possible to give parameters to the callback, `strbuf_expand()` passes a context pointer, which can be used by the programmer of the callback as she sees fit. +`strbuf_expand_dict_cb`:: + + Used as callback for `strbuf_expand()`, expects an array of + struct strbuf_expand_dict_entry as context, i.e. pairs of + placeholder and replacement string. The array needs to be + terminated by an entry with placeholder set to NULL. + +`strbuf_addbuf_percentquote`:: + + Append the contents of one strbuf to another, quoting any + percent signs ("%") into double-percents ("%%") in the + destination. This is useful for literal data to be fed to either + strbuf_expand or to the *printf family of functions. + `strbuf_addf`:: Add a formatted string to the buffer. @@ -213,7 +233,7 @@ which can be used by the programmer of the callback as she sees fit. Read a given size of data from a FILE* pointer to the buffer. + -NOTE: The buffer is rewinded if the read fails. If -1 is returned, +NOTE: The buffer is rewound if the read fails. If -1 is returned, `errno` must be consulted, like you would do for `read(3)`. `strbuf_read()`, `strbuf_read_file()` and `strbuf_getline()` has the same behaviour as well. @@ -228,6 +248,11 @@ same behaviour as well. Read the contents of a file, specified by its path. The third argument can be used to give a hint about the file size, to avoid reallocs. +`strbuf_readlink`:: + + Read the target of a symbolic link, specified by its path. The third + argument can be used to give a hint about the size, to avoid reallocs. + `strbuf_getline`:: Read a line from a FILE* pointer. The second argument specifies the line @@ -239,3 +264,9 @@ same behaviour as well. comments are considered contents to be removed or not. `launch_editor`:: + + Launch the user preferred editor to edit a file and fill the buffer + with the file's contents upon the user completing their editing. The + third argument can be used to set the environment which the editor is + run in. If the buffer is NULL the editor is launched as usual but the + file's contents are not read into the buffer upon completion. diff --git a/Documentation/technical/api-string-list.txt b/Documentation/technical/api-string-list.txt index 293bb15d20..3f575bdcff 100644 --- a/Documentation/technical/api-string-list.txt +++ b/Documentation/technical/api-string-list.txt @@ -38,8 +38,8 @@ struct string_list list; int i; memset(&list, 0, sizeof(struct string_list)); -string_list_append("foo", &list); -string_list_append("bar", &list); +string_list_append(&list, "foo"); +string_list_append(&list, "bar"); for (i = 0; i < list.nr; i++) printf("%s\n", list.items[i].string) ---- @@ -104,8 +104,12 @@ write `string_list_insert(...)->util = ...;`. `unsorted_string_list_has_string`:: It's like `string_list_has_string()` but for unsorted lists. + +`unsorted_string_list_lookup`:: + + It's like `string_list_lookup()` but for unsorted lists. + -This function needs to look through all items, as opposed to its +The above two functions need to look through all items, as opposed to their counterpart for sorted lists, which performs a binary search. Data structures diff --git a/Documentation/technical/api-tree-walking.txt b/Documentation/technical/api-tree-walking.txt index e3ddf91284..14af37c3f1 100644 --- a/Documentation/technical/api-tree-walking.txt +++ b/Documentation/technical/api-tree-walking.txt @@ -1,12 +1,147 @@ tree walking API ================ -Talk about <tree-walk.h>, things like +The tree walking API is used to traverse and inspect trees. -* struct tree_desc -* init_tree_desc -* tree_entry_extract -* update_tree_entry -* get_tree_entry +Data Structures +--------------- -(JC, Linus) +`struct name_entry`:: + + An entry in a tree. Each entry has a sha1 identifier, pathname, and + mode. + +`struct tree_desc`:: + + A semi-opaque data structure used to maintain the current state of the + walk. ++ +* `buffer` is a pointer into the memory representation of the tree. It always +points at the current entry being visited. + +* `size` counts the number of bytes left in the `buffer`. + +* `entry` points to the current entry being visited. + +`struct traverse_info`:: + + A structure used to maintain the state of a traversal. ++ +* `prev` points to the traverse_info which was used to descend into the +current tree. If this is the top-level tree `prev` will point to +a dummy traverse_info. + +* `name` is the entry for the current tree (if the tree is a subtree). + +* `pathlen` is the length of the full path for the current tree. + +* `conflicts` can be used by callbacks to maintain directory-file conflicts. + +* `fn` is a callback called for each entry in the tree. See Traversing for more +information. + +* `data` can be anything the `fn` callback would want to use. + +* `show_all_errors` tells whether to stop at the first error or not. + +Initializing +------------ + +`init_tree_desc`:: + + Initialize a `tree_desc` and decode its first entry. The buffer and + size parameters are assumed to be the same as the buffer and size + members of `struct tree`. + +`fill_tree_descriptor`:: + + Initialize a `tree_desc` and decode its first entry given the sha1 of + a tree. Returns the `buffer` member if the sha1 is a valid tree + identifier and NULL otherwise. + +`setup_traverse_info`:: + + Initialize a `traverse_info` given the pathname of the tree to start + traversing from. The `base` argument is assumed to be the `path` + member of the `name_entry` being recursed into unless the tree is a + top-level tree in which case the empty string ("") is used. + +Walking +------- + +`tree_entry`:: + + Visit the next entry in a tree. Returns 1 when there are more entries + left to visit and 0 when all entries have been visited. This is + commonly used in the test of a while loop. + +`tree_entry_len`:: + + Calculate the length of a tree entry's pathname. This utilizes the + memory structure of a tree entry to avoid the overhead of using a + generic strlen(). + +`update_tree_entry`:: + + Walk to the next entry in a tree. This is commonly used in conjunction + with `tree_entry_extract` to inspect the current entry. + +`tree_entry_extract`:: + + Decode the entry currently being visited (the one pointed to by + `tree_desc's` `entry` member) and return the sha1 of the entry. The + `pathp` and `modep` arguments are set to the entry's pathname and mode + respectively. + +`get_tree_entry`:: + + Find an entry in a tree given a pathname and the sha1 of a tree to + search. Returns 0 if the entry is found and -1 otherwise. The third + and fourth parameters are set to the entry's sha1 and mode + respectively. + +Traversing +---------- + +`traverse_trees`:: + + Traverse `n` number of trees in parallel. The `fn` callback member of + `traverse_info` is called once for each tree entry. + +`traverse_callback_t`:: + The arguments passed to the traverse callback are as follows: ++ +* `n` counts the number of trees being traversed. + +* `mask` has its nth bit set if something exists in the nth entry. + +* `dirmask` has its nth bit set if the nth tree's entry is a directory. + +* `entry` is an array of size `n` where the nth entry is from the nth tree. + +* `info` maintains the state of the traversal. + ++ +Returning a negative value will terminate the traversal. Otherwise the +return value is treated as an update mask. If the nth bit is set the nth tree +will be updated and if the bit is not set the nth tree entry will be the +same in the next callback invocation. + +`make_traverse_path`:: + + Generate the full pathname of a tree entry based from the root of the + traversal. For example, if the traversal has recursed into another + tree named "bar" the pathname of an entry "baz" in the "bar" + tree would be "bar/baz". + +`traverse_path_len`:: + + Calculate the length of a pathname returned by `make_traverse_path`. + This utilizes the memory structure of a tree entry to avoid the + overhead of using a generic strlen(). + +Authors +------- + +Written by Junio C Hamano <gitster@pobox.com> and Linus Torvalds +<torvalds@linux-foundation.org> diff --git a/Documentation/technical/index-format.txt b/Documentation/technical/index-format.txt new file mode 100644 index 0000000000..7b233ca196 --- /dev/null +++ b/Documentation/technical/index-format.txt @@ -0,0 +1,185 @@ +GIT index format +================ + += The git index file has the following format + + All binary numbers are in network byte order. Version 2 is described + here unless stated otherwise. + + - A 12-byte header consisting of + + 4-byte signature: + The signature is { 'D', 'I', 'R', 'C' } (stands for "dircache") + + 4-byte version number: + The current supported versions are 2 and 3. + + 32-bit number of index entries. + + - A number of sorted index entries (see below). + + - Extensions + + Extensions are identified by signature. Optional extensions can + be ignored if GIT does not understand them. + + GIT currently supports cached tree and resolve undo extensions. + + 4-byte extension signature. If the first byte is 'A'..'Z' the + extension is optional and can be ignored. + + 32-bit size of the extension + + Extension data + + - 160-bit SHA-1 over the content of the index file before this + checksum. + +== Index entry + + Index entries are sorted in ascending order on the name field, + interpreted as a string of unsigned bytes (i.e. memcmp() order, no + localization, no special casing of directory separator '/'). Entries + with the same name are sorted by their stage field. + + 32-bit ctime seconds, the last time a file's metadata changed + this is stat(2) data + + 32-bit ctime nanosecond fractions + this is stat(2) data + + 32-bit mtime seconds, the last time a file's data changed + this is stat(2) data + + 32-bit mtime nanosecond fractions + this is stat(2) data + + 32-bit dev + this is stat(2) data + + 32-bit ino + this is stat(2) data + + 32-bit mode, split into (high to low bits) + + 4-bit object type + valid values in binary are 1000 (regular file), 1010 (symbolic link) + and 1110 (gitlink) + + 3-bit unused + + 9-bit unix permission. Only 0755 and 0644 are valid for regular files. + Symbolic links and gitlinks have value 0 in this field. + + 32-bit uid + this is stat(2) data + + 32-bit gid + this is stat(2) data + + 32-bit file size + This is the on-disk size from stat(2), truncated to 32-bit. + + 160-bit SHA-1 for the represented object + + A 16-bit 'flags' field split into (high to low bits) + + 1-bit assume-valid flag + + 1-bit extended flag (must be zero in version 2) + + 2-bit stage (during merge) + + 12-bit name length if the length is less than 0xFFF; otherwise 0xFFF + is stored in this field. + + (Version 3) A 16-bit field, only applicable if the "extended flag" + above is 1, split into (high to low bits). + + 1-bit reserved for future + + 1-bit skip-worktree flag (used by sparse checkout) + + 1-bit intent-to-add flag (used by "git add -N") + + 13-bit unused, must be zero + + Entry path name (variable length) relative to top level directory + (without leading slash). '/' is used as path separator. The special + path components ".", ".." and ".git" (without quotes) are disallowed. + Trailing slash is also disallowed. + + The exact encoding is undefined, but the '.' and '/' characters + are encoded in 7-bit ASCII and the encoding cannot contain a NUL + byte (iow, this is a UNIX pathname). + + 1-8 nul bytes as necessary to pad the entry to a multiple of eight bytes + while keeping the name NUL-terminated. + +== Extensions + +=== Cached tree + + Cached tree extension contains pre-computed hashes for trees that can + be derived from the index. It helps speed up tree object generation + from index for a new commit. + + When a path is updated in index, the path must be invalidated and + removed from tree cache. + + The signature for this extension is { 'T', 'R', 'E', 'E' }. + + A series of entries fill the entire extension; each of which + consists of: + + - NUL-terminated path component (relative to its parent directory); + + - ASCII decimal number of entries in the index that is covered by the + tree this entry represents (entry_count); + + - A space (ASCII 32); + + - ASCII decimal number that represents the number of subtrees this + tree has; + + - A newline (ASCII 10); and + + - 160-bit object name for the object that would result from writing + this span of index as a tree. + + An entry can be in an invalidated state and is represented by having -1 + in the entry_count field. + + The entries are written out in the top-down, depth-first order. The + first entry represents the root level of the repository, followed by the + first subtree---let's call this A---of the root level (with its name + relative to the root level), followed by the first subtree of A (with + its name relative to A), ... + +=== Resolve undo + + A conflict is represented in the index as a set of higher stage entries. + When a conflict is resolved (e.g. with "git add path"), these higher + stage entries will be removed and a stage-0 entry with proper resoluton + is added. + + When these higher stage entries are removed, they are saved in the + resolve undo extension, so that conflicts can be recreated (e.g. with + "git checkout -m"), in case users want to redo a conflict resolution + from scratch. + + The signature for this extension is { 'R', 'E', 'U', 'C' }. + + A series of entries fill the entire extension; each of which + consists of: + + - NUL-terminated pathname the entry describes (relative to the root of + the repository, i.e. full pathname); + + - Three NUL-terminated ASCII octal numbers, entry mode of entries in + stage 1 to 3 (a missing stage is represented by "0" in this field); + and + + - At most three 160-bit object names of the entry in stages from 1 to 3 + (nothing is written for a missing stage). + diff --git a/Documentation/technical/pack-protocol.txt b/Documentation/technical/pack-protocol.txt index 9cd48b4859..369f91d3b9 100644 --- a/Documentation/technical/pack-protocol.txt +++ b/Documentation/technical/pack-protocol.txt @@ -1,41 +1,494 @@ -Pack transfer protocols -======================= - -There are two Pack push-pull protocols. - -upload-pack (S) | fetch/clone-pack (C) protocol: - - # Tell the puller what commits we have and what their names are - S: SHA1 name - S: ... - S: SHA1 name - S: # flush -- it's your turn - # Tell the pusher what commits we want, and what we have - C: want name - C: .. - C: want name - C: have SHA1 - C: have SHA1 - C: ... - C: # flush -- occasionally ask "had enough?" - S: NAK - C: have SHA1 - C: ... - C: have SHA1 - S: ACK - C: done - S: XXXXXXX -- packfile contents. - -send-pack | receive-pack protocol. - - # Tell the pusher what commits we have and what their names are - C: SHA1 name - C: ... - C: SHA1 name - C: # flush -- it's your turn - # Tell the puller what the pusher has - S: old-SHA1 new-SHA1 name - S: old-SHA1 new-SHA1 name - S: ... - S: # flush -- done with the list - S: XXXXXXX --- packfile contents. +Packfile transfer protocols +=========================== + +Git supports transferring data in packfiles over the ssh://, git:// and +file:// transports. There exist two sets of protocols, one for pushing +data from a client to a server and another for fetching data from a +server to a client. All three transports (ssh, git, file) use the same +protocol to transfer data. + +The processes invoked in the canonical Git implementation are 'upload-pack' +on the server side and 'fetch-pack' on the client side for fetching data; +then 'receive-pack' on the server and 'send-pack' on the client for pushing +data. The protocol functions to have a server tell a client what is +currently on the server, then for the two to negotiate the smallest amount +of data to send in order to fully update one or the other. + +Transports +---------- +There are three transports over which the packfile protocol is +initiated. The Git transport is a simple, unauthenticated server that +takes the command (almost always 'upload-pack', though Git +servers can be configured to be globally writable, in which 'receive- +pack' initiation is also allowed) with which the client wishes to +communicate and executes it and connects it to the requesting +process. + +In the SSH transport, the client just runs the 'upload-pack' +or 'receive-pack' process on the server over the SSH protocol and then +communicates with that invoked process over the SSH connection. + +The file:// transport runs the 'upload-pack' or 'receive-pack' +process locally and communicates with it over a pipe. + +Git Transport +------------- + +The Git transport starts off by sending the command and repository +on the wire using the pkt-line format, followed by a NUL byte and a +hostname parameter, terminated by a NUL byte. + + 0032git-upload-pack /project.git\0host=myserver.com\0 + +-- + git-proto-request = request-command SP pathname NUL [ host-parameter NUL ] + request-command = "git-upload-pack" / "git-receive-pack" / + "git-upload-archive" ; case sensitive + pathname = *( %x01-ff ) ; exclude NUL + host-parameter = "host=" hostname [ ":" port ] +-- + +Only host-parameter is allowed in the git-proto-request. Clients +MUST NOT attempt to send additional parameters. It is used for the +git-daemon name based virtual hosting. See --interpolated-path +option to git daemon, with the %H/%CH format characters. + +Basically what the Git client is doing to connect to an 'upload-pack' +process on the server side over the Git protocol is this: + + $ echo -e -n \ + "0039git-upload-pack /schacon/gitbook.git\0host=example.com\0" | + nc -v example.com 9418 + + +SSH Transport +------------- + +Initiating the upload-pack or receive-pack processes over SSH is +executing the binary on the server via SSH remote execution. +It is basically equivalent to running this: + + $ ssh git.example.com "git-upload-pack '/project.git'" + +For a server to support Git pushing and pulling for a given user over +SSH, that user needs to be able to execute one or both of those +commands via the SSH shell that they are provided on login. On some +systems, that shell access is limited to only being able to run those +two commands, or even just one of them. + +In an ssh:// format URI, it's absolute in the URI, so the '/' after +the host name (or port number) is sent as an argument, which is then +read by the remote git-upload-pack exactly as is, so it's effectively +an absolute path in the remote filesystem. + + git clone ssh://user@example.com/project.git + | + v + ssh user@example.com "git-upload-pack '/project.git'" + +In a "user@host:path" format URI, its relative to the user's home +directory, because the Git client will run: + + git clone user@example.com:project.git + | + v + ssh user@example.com "git-upload-pack 'project.git'" + +The exception is if a '~' is used, in which case +we execute it without the leading '/'. + + ssh://user@example.com/~alice/project.git, + | + v + ssh user@example.com "git-upload-pack '~alice/project.git'" + +A few things to remember here: + +- The "command name" is spelled with dash (e.g. git-upload-pack), but + this can be overridden by the client; + +- The repository path is always quoted with single quotes. + +Fetching Data From a Server +=========================== + +When one Git repository wants to get data that a second repository +has, the first can 'fetch' from the second. This operation determines +what data the server has that the client does not then streams that +data down to the client in packfile format. + + +Reference Discovery +------------------- + +When the client initially connects the server will immediately respond +with a listing of each reference it has (all branches and tags) along +with the object name that each reference currently points to. + + $ echo -e -n "0039git-upload-pack /schacon/gitbook.git\0host=example.com\0" | + nc -v example.com 9418 + 00887217a7c7e582c46cec22a130adf4b9d7d950fba0 HEAD\0multi_ack thin-pack side-band side-band-64k ofs-delta shallow no-progress include-tag + 00441d3fcd5ced445d1abc402225c0b8a1299641f497 refs/heads/integration + 003f7217a7c7e582c46cec22a130adf4b9d7d950fba0 refs/heads/master + 003cb88d2441cac0977faf98efc80305012112238d9d refs/tags/v0.9 + 003c525128480b96c89e6418b1e40909bf6c5b2d580f refs/tags/v1.0 + 003fe92df48743b7bc7d26bcaabfddde0a1e20cae47c refs/tags/v1.0^{} + 0000 + +Server SHOULD terminate each non-flush line using LF ("\n") terminator; +client MUST NOT complain if there is no terminator. + +The returned response is a pkt-line stream describing each ref and +its current value. The stream MUST be sorted by name according to +the C locale ordering. + +If HEAD is a valid ref, HEAD MUST appear as the first advertised +ref. If HEAD is not a valid ref, HEAD MUST NOT appear in the +advertisement list at all, but other refs may still appear. + +The stream MUST include capability declarations behind a NUL on the +first ref. The peeled value of a ref (that is "ref^{}") MUST be +immediately after the ref itself, if presented. A conforming server +MUST peel the ref if it's an annotated tag. + +---- + advertised-refs = (no-refs / list-of-refs) + flush-pkt + + no-refs = PKT-LINE(zero-id SP "capabilities^{}" + NUL capability-list LF) + + list-of-refs = first-ref *other-ref + first-ref = PKT-LINE(obj-id SP refname + NUL capability-list LF) + + other-ref = PKT-LINE(other-tip / other-peeled) + other-tip = obj-id SP refname LF + other-peeled = obj-id SP refname "^{}" LF + + capability-list = capability *(SP capability) + capability = 1*(LC_ALPHA / DIGIT / "-" / "_") + LC_ALPHA = %x61-7A +---- + +Server and client MUST use lowercase for obj-id, both MUST treat obj-id +as case-insensitive. + +See protocol-capabilities.txt for a list of allowed server capabilities +and descriptions. + +Packfile Negotiation +-------------------- +After reference and capabilities discovery, the client can decide +to terminate the connection by sending a flush-pkt, telling the +server it can now gracefully terminate (as happens with the ls-remote +command) or it can enter the negotiation phase, where the client and +server determine what the minimal packfile necessary for transport is. + +Once the client has the initial list of references that the server +has, as well as the list of capabilities, it will begin telling the +server what objects it wants and what objects it has, so the server +can make a packfile that only contains the objects that the client needs. +The client will also send a list of the capabilities it wants to be in +effect, out of what the server said it could do with the first 'want' line. + +---- + upload-request = want-list + have-list + compute-end + + want-list = first-want + *additional-want + flush-pkt + + first-want = PKT-LINE("want" SP obj-id SP capability-list LF) + additional-want = PKT-LINE("want" SP obj-id LF) + + have-list = *have-line + have-line = PKT-LINE("have" SP obj-id LF) + compute-end = flush-pkt / PKT-LINE("done") +---- + +Clients MUST send all the obj-ids it wants from the reference +discovery phase as 'want' lines. Clients MUST send at least one +'want' command in the request body. Clients MUST NOT mention an +obj-id in a 'want' command which did not appear in the response +obtained through ref discovery. + +If client is requesting a shallow clone, it will now send a 'deepen' +line with the depth it is requesting. + +Once all the "want"s (and optional 'deepen') are transferred, +clients MUST send a flush-pkt. If the client has all the references +on the server, client flushes and disconnects. + +TODO: shallow/unshallow response and document the deepen command in the ABNF. + +Now the client will send a list of the obj-ids it has using 'have' +lines. In multi_ack mode, the canonical implementation will send up +to 32 of these at a time, then will send a flush-pkt. The canonical +implementation will skip ahead and send the next 32 immediately, +so that there is always a block of 32 "in-flight on the wire" at a +time. + +If the server reads 'have' lines, it then will respond by ACKing any +of the obj-ids the client said it had that the server also has. The +server will ACK obj-ids differently depending on which ack mode is +chosen by the client. + +In multi_ack mode: + + * the server will respond with 'ACK obj-id continue' for any common + commits. + + * once the server has found an acceptable common base commit and is + ready to make a packfile, it will blindly ACK all 'have' obj-ids + back to the client. + + * the server will then send a 'NACK' and then wait for another response + from the client - either a 'done' or another list of 'have' lines. + +In multi_ack_detailed mode: + + * the server will differentiate the ACKs where it is signaling + that it is ready to send data with 'ACK obj-id ready' lines, and + signals the identified common commits with 'ACK obj-id common' lines. + +Without either multi_ack or multi_ack_detailed: + + * upload-pack sends "ACK obj-id" on the first common object it finds. + After that it says nothing until the client gives it a "done". + + * upload-pack sends "NAK" on a flush-pkt if no common object + has been found yet. If one has been found, and thus an ACK + was already sent, it's silent on the flush-pkt. + +After the client has gotten enough ACK responses that it can determine +that the server has enough information to send an efficient packfile +(in the canonical implementation, this is determined when it has received +enough ACKs that it can color everything left in the --date-order queue +as common with the server, or the --date-order queue is empty), or the +client determines that it wants to give up (in the canonical implementation, +this is determined when the client sends 256 'have' lines without getting +any of them ACKed by the server - meaning there is nothing in common and +the server should just send all of its objects), then the client will send +a 'done' command. The 'done' command signals to the server that the client +is ready to receive its packfile data. + +However, the 256 limit *only* turns on in the canonical client +implementation if we have received at least one "ACK %s continue" +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 +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. + +Then the server will start sending its packfile data. + +---- + server-response = *ack_multi ack / nak + ack_multi = PKT-LINE("ACK" SP obj-id ack_status LF) + ack_status = "continue" / "common" / "ready" + ack = PKT-LINE("ACK SP obj-id LF) + nak = PKT-LINE("NAK" LF) +---- + +A simple clone may look like this (with no 'have' lines): + +---- + C: 0054want 74730d410fcb6603ace96f1dc55ea6196122532d\0multi_ack \ + side-band-64k ofs-delta\n + C: 0032want 7d1665144a3a975c05f1f43902ddaf084e784dbe\n + C: 0032want 5a3f6be755bbb7deae50065988cbfa1ffa9ab68a\n + C: 0032want 7e47fe2bd8d01d481f44d7af0531bd93d3b21c01\n + C: 0032want 74730d410fcb6603ace96f1dc55ea6196122532d\n + C: 0000 + C: 0009done\n + + S: 0008NAK\n + S: [PACKFILE] +---- + +An incremental update (fetch) response might look like this: + +---- + C: 0054want 74730d410fcb6603ace96f1dc55ea6196122532d\0multi_ack \ + side-band-64k ofs-delta\n + C: 0032want 7d1665144a3a975c05f1f43902ddaf084e784dbe\n + C: 0032want 5a3f6be755bbb7deae50065988cbfa1ffa9ab68a\n + C: 0000 + C: 0032have 7e47fe2bd8d01d481f44d7af0531bd93d3b21c01\n + C: [30 more have lines] + C: 0032have 74730d410fcb6603ace96f1dc55ea6196122532d\n + C: 0000 + + S: 003aACK 7e47fe2bd8d01d481f44d7af0531bd93d3b21c01 continue\n + S: 003aACK 74730d410fcb6603ace96f1dc55ea6196122532d continue\n + S: 0008NAK\n + + C: 0009done\n + + S: 0031ACK 74730d410fcb6603ace96f1dc55ea6196122532d\n + S: [PACKFILE] +---- + + +Packfile Data +------------- + +Now that the client and server have finished negotiation about what +the minimal amount of data that needs to be sent to the client is, the server +will construct and send the required data in packfile format. + +See pack-format.txt for what the packfile itself actually looks like. + +If 'side-band' or 'side-band-64k' capabilities have been specified by +the client, the server will send the packfile data multiplexed. + +Each packet starting with the packet-line length of the amount of data +that follows, followed by a single byte specifying the sideband the +following data is coming in on. + +In 'side-band' mode, it will send up to 999 data bytes plus 1 control +code, for a total of up to 1000 bytes in a pkt-line. In 'side-band-64k' +mode it will send up to 65519 data bytes plus 1 control code, for a +total of up to 65520 bytes in a pkt-line. + +The sideband byte will be a '1', '2' or a '3'. Sideband '1' will contain +packfile data, sideband '2' will be used for progress information that the +client will generally print to stderr and sideband '3' is used for error +information. + +If no 'side-band' capability was specified, the server will stream the +entire packfile without multiplexing. + + +Pushing Data To a Server +======================== + +Pushing data to a server will invoke the 'receive-pack' process on the +server, which will allow the client to tell it which references it should +update and then send all the data the server will need for those new +references to be complete. Once all the data is received and validated, +the server will then update its references to what the client specified. + +Authentication +-------------- + +The protocol itself contains no authentication mechanisms. That is to be +handled by the transport, such as SSH, before the 'receive-pack' process is +invoked. If 'receive-pack' is configured over the Git transport, those +repositories will be writable by anyone who can access that port (9418) as +that transport is unauthenticated. + +Reference Discovery +------------------- + +The reference discovery phase is done nearly the same way as it is in the +fetching protocol. Each reference obj-id and name on the server is sent +in packet-line format to the client, followed by a flush-pkt. The only +real difference is that the capability listing is different - the only +possible values are 'report-status', 'delete-refs' and 'ofs-delta'. + +Reference Update Request and Packfile Transfer +---------------------------------------------- + +Once the client knows what references the server is at, it can send a +list of reference update requests. For each reference on the server +that it wants to update, it sends a line listing the obj-id currently on +the server, the obj-id the client would like to update it to and the name +of the reference. + +This list is followed by a flush-pkt and then the packfile that should +contain all the objects that the server will need to complete the new +references. + +---- + update-request = command-list [pack-file] + + command-list = PKT-LINE(command NUL capability-list LF) + *PKT-LINE(command LF) + flush-pkt + + command = create / delete / update + create = zero-id SP new-id SP name + delete = old-id SP zero-id SP name + update = old-id SP new-id SP name + + old-id = obj-id + new-id = obj-id + + pack-file = "PACK" 28*(OCTET) +---- + +If the receiving end does not support delete-refs, the sending end MUST +NOT ask for delete command. + +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, +even if the server already has all the necessary objects. In this +case the client MUST send an empty pack-file. The only time this +is likely to happen is if the client is creating +a new branch or a tag that points to an existing obj-id. + +The server will receive the packfile, unpack it, then validate each +reference that is being updated that it hasn't changed while the request +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. + +Report Status +------------- + +After receiving the pack data from the sender, the receiver sends a +report if 'report-status' capability is in effect. +It is a short listing of what happened in that update. It will first +list the status of the packfile unpacking as either 'unpack ok' or +'unpack [error]'. Then it will list the status for each of the references +that it tried to update. Each line is either 'ok [refname]' if the +update was successful, or 'ng [refname] [error]' if the update was not. + +---- + report-status = unpack-status + 1*(command-status) + flush-pkt + + unpack-status = PKT-LINE("unpack" SP unpack-result LF) + unpack-result = "ok" / error-msg + + command-status = command-ok / command-fail + command-ok = PKT-LINE("ok" SP refname LF) + command-fail = PKT-LINE("ng" SP refname SP error-msg LF) + + error-msg = 1*(OCTECT) ; where not "ok" +---- + +Updates can be unsuccessful for a number of reasons. The reference can have +changed since the reference discovery phase was originally sent, meaning +someone pushed in the meantime. The reference being pushed could be a +non-fast-forward reference and the update hooks or configuration could be +set to not allow that, etc. Also, some references can be updated while others +can be rejected. + +An example client/server communication might look like this: + +---- + S: 007c74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/local\0report-status delete-refs ofs-delta\n + S: 003e7d1665144a3a975c05f1f43902ddaf084e784dbe refs/heads/debug\n + S: 003f74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/master\n + S: 003f74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/team\n + S: 0000 + + C: 003e7d1665144a3a975c05f1f43902ddaf084e784dbe 74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/debug\n + C: 003e74730d410fcb6603ace96f1dc55ea6196122532d 5a3f6be755bbb7deae50065988cbfa1ffa9ab68a refs/heads/master\n + C: 0000 + C: [PACKDATA] + + S: 000eunpack ok\n + S: 0018ok refs/heads/debug\n + S: 002ang refs/heads/master non-fast-forward\n +---- diff --git a/Documentation/technical/protocol-capabilities.txt b/Documentation/technical/protocol-capabilities.txt new file mode 100644 index 0000000000..b15517fa06 --- /dev/null +++ b/Documentation/technical/protocol-capabilities.txt @@ -0,0 +1,187 @@ +Git Protocol Capabilities +========================= + +Servers SHOULD support all capabilities defined in this document. + +On the very first line of the initial server response of either +receive-pack and upload-pack the first reference is followed by +a NUL byte and then a list of space delimited server capabilities. +These allow the server to declare what it can and cannot support +to the client. + +Client will then send a space separated list of capabilities it wants +to be in effect. The client MUST NOT ask for capabilities the server +did not say it supports. + +Server MUST diagnose and abort if capabilities it does not understand +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' and 'delete-refs' capabilities are sent and +recognized by the receive-pack (push to server) process. + +The 'ofs-delta' capability is sent and recognized by both upload-pack +and receive-pack protocols. + +All other capabilities are only recognized by the upload-pack (fetch +from server) process. + +multi_ack +--------- + +The 'multi_ack' capability allows the server to return "ACK obj-id +continue" as soon as it finds a commit that it can use as a common +base, between the client's wants and the client's have set. + +By sending this early, the server can potentially head off the client +from walking any further down that particular branch of the client's +repository history. The client may still need to walk down other +branches, sending have lines for those, until the server has a +complete cut across the DAG, or the client has said "done". + +Without multi_ack, a client sends have lines in --date-order until +the server has found a common base. That means the client will send +have lines that are already known by the server to be common, because +they overlap in time with another branch that the server hasn't found +a common base on yet. + +For example suppose the client has commits in caps that the server +doesn't and the server has commits in lower case that the client +doesn't, as in the following diagram: + + +---- u ---------------------- x + / +----- y + / / + a -- b -- c -- d -- E -- F + \ + +--- Q -- R -- S + +If the client wants x,y and starts out by saying have F,S, the server +doesn't know what F,S is. Eventually the client says "have d" and +the server sends "ACK d continue" to let the client know to stop +walking down that line (so don't send c-b-a), but it's not done yet, +it needs a base for x. The client keeps going with S-R-Q, until a +gets reached, at which point the server has a clear base and it all +ends. + +Without multi_ack the client would have sent that c-b-a chain anyway, +interleaved with S-R-Q. + +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. + +Client MUST NOT request 'thin-pack' capability if it cannot turn a thin +pack into a self-contained pack. + + +side-band, side-band-64k +------------------------ + +This capability means that server can send, and client understand multiplexed +progress reports and error info interleaved with the packfile itself. + +These two options are mutually exclusive. A modern client always +favors 'side-band-64k'. + +Either mode indicates that the packfile data will be streamed broken +up into packets of up to either 1000 bytes in the case of 'side_band', +or 65520 bytes in the case of 'side_band_64k'. Each packet is made up +of a leading 4-byte pkt-line length of how much data is in the packet, +followed by a 1-byte stream code, followed by the actual data. + +The stream code can be one of: + + 1 - pack data + 2 - progress messages + 3 - fatal error message just before stream aborts + +The "side-band-64k" capability came about as a way for newer clients +that can handle much larger packets to request packets that are +actually crammed nearly full, while maintaining backward compatibility +for the older clients. + +Further, with side-band and its up to 1000-byte messages, it's actually +999 bytes of payload and 1 byte for the stream code. With side-band-64k, +same deal, you have up to 65519 bytes of data and 1 byte for the stream +code. + +The client MUST send only maximum of one of "side-band" and "side- +band-64k". Server MUST diagnose it as an error if client requests +both. + +ofs-delta +--------- + +Server can send, and client understand PACKv2 with delta referring to +its base by position in pack rather than by an obj-id. That is, they can +send/read OBJ_OFS_DELTA (aka type 6) in a packfile. + +shallow +------- + +This capability adds "deepen", "shallow" and "unshallow" commands to +the fetch-pack/upload-pack protocol so clients can request shallow +clones. + +no-progress +----------- + +The client was started with "git clone -q" or something, and doesn't +want that side band 2. Basically the client just says "I do not +wish to receive stream 2 on sideband, so do not send it to me, and if +you did, I will drop it on the floor anyway". However, the sideband +channel 3 is still used for error responses. + +include-tag +----------- + +The 'include-tag' capability is about sending annotated tags if we are +sending objects they point to. If we pack an object to the client, and +a tag object points exactly at that object, we pack the tag object too. +In general this allows a client to get all new annotated tags when it +fetches a branch, in a single network connection. + +Clients MAY always send include-tag, hardcoding it into a request when +the server advertises this capability. The decision for a client to +request include-tag only has to do with the client's desires for tag +data, whether or not a server had advertised objects in the +refs/tags/* namespace. + +Servers MUST pack the tags if their referrant is packed and the client +has requested include-tags. + +Clients MUST be prepared for the case where a server has ignored +include-tag and has not actually sent tags in the pack. In such +cases the client SHOULD issue a subsequent fetch to acquire the tags +that include-tag would have otherwise given the client. + +The server SHOULD send include-tag, if it supports it, regardless +of whether or not there are tags available. + +report-status +------------- + +The upload-pack process can receive a 'report-status' capability, +which tells it that the client wants a report of what happened after +a packfile upload and reference update. If the pushing client requests +this capability, after unpacking and updating references the server +will respond with whether the packfile unpacked successfully and if +each reference was updated successfully. If any of those were not +successful, it will send back an error message. See pack-protocol.txt +for example messages. + +delete-refs +----------- + +If the server sends back the 'delete-refs' capability, it means that +it is capable of accepting a zero-id value as the target +value of a reference update. It is not sent back by the client, it +simply informs the client that it can be sent zero-id values +to delete references. diff --git a/Documentation/technical/protocol-common.txt b/Documentation/technical/protocol-common.txt new file mode 100644 index 0000000000..d30a1b9510 --- /dev/null +++ b/Documentation/technical/protocol-common.txt @@ -0,0 +1,96 @@ +Documentation Common to Pack and Http Protocols +=============================================== + +ABNF Notation +------------- + +ABNF notation as described by RFC 5234 is used within the protocol documents, +except the following replacement core rules are used: +---- + HEXDIG = DIGIT / "a" / "b" / "c" / "d" / "e" / "f" +---- + +We also define the following common rules: +---- + NUL = %x00 + zero-id = 40*"0" + obj-id = 40*(HEXDIGIT) + + refname = "HEAD" + refname /= "refs/" <see discussion below> +---- + +A refname is a hierarchical octet string beginning with "refs/" and +not violating the 'git-check-ref-format' command's validation rules. +More specifically, they: + +. They can include slash `/` for hierarchical (directory) + grouping, but no slash-separated component can begin with a + dot `.`. + +. They must contain at least one `/`. This enforces the presence of a + category like `heads/`, `tags/` etc. but the actual names are not + restricted. + +. They cannot have two consecutive dots `..` anywhere. + +. They cannot have ASCII control characters (i.e. bytes whose + values are lower than \040, or \177 `DEL`), space, tilde `~`, + caret `{caret}`, colon `:`, question-mark `?`, asterisk `*`, + or open bracket `[` anywhere. + +. They cannot end with a slash `/` nor a dot `.`. + +. They cannot end with the sequence `.lock`. + +. They cannot contain a sequence `@{`. + +. They cannot contain a `\\`. + + +pkt-line Format +--------------- + +Much (but not all) of the payload is described around pkt-lines. + +A pkt-line is a variable length binary string. The first four bytes +of the line, the pkt-len, indicates the total length of the line, +in hexadecimal. The pkt-len includes the 4 bytes used to contain +the length's hexadecimal representation. + +A pkt-line MAY contain binary data, so implementors MUST ensure +pkt-line parsing/formatting routines are 8-bit clean. + +A non-binary line SHOULD BE terminated by an LF, which if present +MUST be included in the total length. + +The maximum length of a pkt-line's data component is 65520 bytes. +Implementations MUST NOT send pkt-line whose length exceeds 65524 +(65520 bytes of payload + 4 bytes of length data). + +Implementations SHOULD NOT send an empty pkt-line ("0004"). + +A pkt-line with a length field of 0 ("0000"), called a flush-pkt, +is a special case and MUST be handled differently than an empty +pkt-line ("0004"). + +---- + pkt-line = data-pkt / flush-pkt + + data-pkt = pkt-len pkt-payload + pkt-len = 4*(HEXDIG) + pkt-payload = (pkt-len - 4)*(OCTET) + + flush-pkt = "0000" +---- + +Examples (as C-style strings): + +---- + pkt-line actual value + --------------------------------- + "0006a\n" "a\n" + "0005a" "a" + "000bfoobar\n" "foobar\n" + "0004" "" +---- diff --git a/Documentation/technical/racy-git.txt b/Documentation/technical/racy-git.txt index 6bdf034b3a..53aa0c82c2 100644 --- a/Documentation/technical/racy-git.txt +++ b/Documentation/technical/racy-git.txt @@ -42,10 +42,12 @@ compared, but this is not enabled by default because this member is not stable on network filesystems. With `USE_NSEC` compile-time option, `st_mtim.tv_nsec` and `st_ctim.tv_nsec` members are also compared, but this is not enabled by default -because the value of this member becomes meaningless once the -inode is evicted from the inode cache on filesystems that do not -store it on disk. - +because in-core timestamps can have finer granularity than +on-disk timestamps, resulting in meaningless changes when an +inode is evicted from the inode cache. See commit 8ce13b0 +of git://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git +([PATCH] Sync in core time granuality with filesystems, +2005-01-04). Racy git -------- @@ -135,7 +137,7 @@ them, and give the same timestamp to the index file: This will make all index entries racily clean. The linux-2.6 project, for example, there are over 20,000 files in the working -tree. On my Athron 64X2 3800+, after the above: +tree. On my Athlon 64 X2 3800+, after the above: $ /usr/bin/time git diff-files 1.68user 0.54system 0:02.22elapsed 100%CPU (0avgtext+0avgdata 0maxresident)k |