diff options
Diffstat (limited to 'Documentation/technical')
| -rw-r--r-- | Documentation/technical/api-error-handling.txt | 75 | ||||
| -rw-r--r-- | Documentation/technical/api-strbuf.txt | 351 | ||||
| -rw-r--r-- | Documentation/technical/pack-protocol.txt | 16 | ||||
| -rw-r--r-- | Documentation/technical/protocol-capabilities.txt | 13 |
4 files changed, 94 insertions, 361 deletions
diff --git a/Documentation/technical/api-error-handling.txt b/Documentation/technical/api-error-handling.txt new file mode 100644 index 0000000000..ceeedd485c --- /dev/null +++ b/Documentation/technical/api-error-handling.txt @@ -0,0 +1,75 @@ +Error reporting in git +====================== + +`die`, `usage`, `error`, and `warning` report errors of various +kinds. + +- `die` is for fatal application errors. It prints a message to + the user and exits with status 128. + +- `usage` is for errors in command line usage. After printing its + message, it exits with status 129. (See also `usage_with_options` + in the link:api-parse-options.html[parse-options API].) + +- `error` is for non-fatal library errors. It prints a message + to the user and returns -1 for convenience in signaling the error + to the caller. + +- `warning` is for reporting situations that probably should not + occur but which the user (and Git) can continue to work around + without running into too many problems. Like `error`, it + returns -1 after reporting the situation to the caller. + +Customizable error handlers +--------------------------- + +The default behavior of `die` and `error` is to write a message to +stderr and then exit or return as appropriate. This behavior can be +overridden using `set_die_routine` and `set_error_routine`. For +example, "git daemon" uses set_die_routine to write the reason `die` +was called to syslog before exiting. + +Library errors +-------------- + +Functions return a negative integer on error. Details beyond that +vary from function to function: + +- Some functions return -1 for all errors. Others return a more + specific value depending on how the caller might want to react + to the error. + +- Some functions report the error to stderr with `error`, + while others leave that for the caller to do. + +- errno is not meaningful on return from most functions (except + for thin wrappers for system calls). + +Check the function's API documentation to be sure. + +Caller-handled errors +--------------------- + +An increasing number of functions take a parameter 'struct strbuf *err'. +On error, such functions append a message about what went wrong to the +'err' strbuf. The message is meant to be complete enough to be passed +to `die` or `error` as-is. For example: + + if (ref_transaction_commit(transaction, &err)) + die("%s", err.buf); + +The 'err' parameter will be untouched if no error occurred, so multiple +function calls can be chained: + + t = ref_transaction_begin(&err); + if (!t || + ref_transaction_update(t, "HEAD", ..., &err) || + ret_transaction_commit(t, &err)) + die("%s", err.buf); + +The 'err' parameter must be a pointer to a valid strbuf. To silence +a message, pass a strbuf that is explicitly ignored: + + if (thing_that_can_fail_in_an_ignorable_way(..., &err)) + /* This failure is okay. */ + strbuf_reset(&err); diff --git a/Documentation/technical/api-strbuf.txt b/Documentation/technical/api-strbuf.txt deleted file mode 100644 index cca6543234..0000000000 --- a/Documentation/technical/api-strbuf.txt +++ /dev/null @@ -1,351 +0,0 @@ -strbuf API -========== - -strbuf's are meant to be used with all the usual C string and memory -APIs. Given that the length of the buffer is known, it's often better to -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. - -A strbuf is NUL terminated for convenience, but no function in the -strbuf API actually relies on the string being free of NULs. - -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 -`strbuf_init()` or by `= STRBUF_INIT` before the invariants, though. -+ -Do *not* assume anything on what `buf` really is (e.g. if it is -allocated memory or not), use `strbuf_detach()` to unwrap a memory -buffer from its strbuf shell in a safe way. That is the sole supported -way. This will give you a malloced buffer that you can later `free()`. -+ -However, it is totally safe to modify anything in the string pointed by -the `buf` member, between the indices `0` and `len-1` (inclusive). - -. The `buf` member is a byte array that has at least `len + 1` bytes - allocated. The extra byte is used to store a `'\0'`, allowing the - `buf` member to be a valid C-string. Every strbuf function ensure this - invariant is preserved. -+ -NOTE: It is OK to "play" with the buffer directly if you work it this - way: -+ ----- -strbuf_grow(sb, SOME_SIZE); <1> -strbuf_setlen(sb, sb->len + SOME_OTHER_SIZE); ----- -<1> Here, the memory array starting at `sb->buf`, and of length -`strbuf_avail(sb)` is all yours, and you can be sure that -`strbuf_avail(sb)` is at least `SOME_SIZE`. -+ -NOTE: `SOME_OTHER_SIZE` must be smaller or equal to `strbuf_avail(sb)`. -+ -Doing so is safe, though if it has to be done in many places, adding the -missing API to the strbuf module is the way to go. -+ -WARNING: Do _not_ assume that the area that is yours is of size `alloc -- 1` even if it's true in the current implementation. Alloc is somehow a -"private" member that should not be messed with. Use `strbuf_avail()` -instead. - -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. - -Functions ---------- - -* Life cycle - -`strbuf_init`:: - - Initialize the structure. The second parameter can be zero or a bigger - number to allocate memory, in case you want to prevent further reallocs. - -`strbuf_release`:: - - Release a string buffer and the memory it used. You should not use the - string buffer after using this function, unless you initialize it again. - -`strbuf_detach`:: - - Detach the string from the strbuf and returns it; you now own the - storage the string occupies and it is your responsibility from then on - to release it with `free(3)` when you are done with it. - -`strbuf_attach`:: - - Attach a string to a buffer. You should specify the string to attach, - the current length of the string and the amount of allocated memory. - The amount must be larger than the string length, because the string you - pass is supposed to be a NUL-terminated string. This string _must_ be - malloc()ed, and after attaching, the pointer cannot be relied upon - anymore, and neither be free()d directly. - -`strbuf_swap`:: - - Swap the contents of two string buffers. - -* Related to the size of the buffer - -`strbuf_avail`:: - - Determine the amount of allocated but unused memory. - -`strbuf_grow`:: - - Ensure that at least this amount of unused memory is available after - `len`. This is used when you know a typical size for what you will add - and want to avoid repetitive automatic resizing of the underlying buffer. - This is never a needed operation, but can be critical for performance in - some cases. - -`strbuf_setlen`:: - - Set the length of the buffer to a given value. This function does *not* - allocate new memory, so you should not perform a `strbuf_setlen()` to a - length that is larger than `len + strbuf_avail()`. `strbuf_setlen()` is - just meant as a 'please fix invariants from this strbuf I just messed - with'. - -`strbuf_reset`:: - - Empty the buffer by setting the size of it to zero. - -* 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 - than zero if the first buffer is found, respectively, to be less than, - to match, or be greater than the second buffer. - -* Adding data to the buffer - -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`:: - - 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 - will be shifted, not overwritten. - -`strbuf_remove`:: - - Remove given amount of data from a given position of the buffer. - -`strbuf_splice`:: - - Remove the bytes between `pos..pos+len` and replace it with the given - data. - -`strbuf_add_commented_lines`:: - - Add a NUL-terminated string to the buffer. Each line will be prepended - by a comment character and a blank. - -`strbuf_add`:: - - Add data of given length to the buffer. - -`strbuf_addstr`:: - -Add a NUL-terminated string to the buffer. -+ -NOTE: This function will *always* be implemented as an inline or a macro -that expands to: -+ ----- -strbuf_add(..., s, strlen(s)); ----- -+ -Meaning that this is efficient to write things like: -+ ----- -strbuf_addstr(sb, "immediate string"); ----- - -`strbuf_addbuf`:: - - Copy the contents of another buffer at the end of the current one. - -`strbuf_adddup`:: - - Copy part of the buffer from a given position till a given length to the - end of the buffer. - -`strbuf_expand`:: - - This function can be used to expand a format string containing - placeholders. To that end, it parses the string and calls the specified - function for every percent sign found. -+ -The callback function is given a pointer to the character after the `%` -and a pointer to the struct strbuf. It is expected to add the expanded -version of the placeholder to the strbuf, e.g. to add a newline -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. -+ -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_humanise_bytes`:: - - Append the given byte size as a human-readable string (i.e. 12.23 KiB, - 3.50 MiB). - -`strbuf_addf`:: - - Add a formatted string to the buffer. - -`strbuf_commented_addf`:: - - Add a formatted string prepended by a comment character and a - blank to the buffer. - -`strbuf_fread`:: - - Read a given size of data from a FILE* pointer to the buffer. -+ -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. - -`strbuf_read`:: - - Read the contents of a given file descriptor. The third argument can be - used to give a hint about the file size, to avoid reallocs. - -`strbuf_read_file`:: - - 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 *, overwriting the existing contents - of the strbuf. The second argument specifies the line - terminator character, typically `'\n'`. - Reading stops after the terminator or at EOF. The terminator - is removed from the buffer before returning. Returns 0 unless - there was nothing left before EOF, in which case it returns `EOF`. - -`strbuf_getwholeline`:: - - Like `strbuf_getline`, but keeps the trailing terminator (if - any) in the buffer. - -`strbuf_getwholeline_fd`:: - - Like `strbuf_getwholeline`, but operates on a file descriptor. - It reads one character at a time, so it is very slow. Do not - 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 - comments are considered contents to be removed or not. - -`strbuf_split_buf`:: -`strbuf_split_str`:: -`strbuf_split_max`:: -`strbuf_split`:: - - Split a string or strbuf into a list of strbufs at a specified - terminator character. The returned substrings include the - terminator characters. Some of these functions take a `max` - parameter, which, if positive, limits the output to that - number of substrings. - -`strbuf_list_free`:: - - Free a list of strbufs (for example, the return values of the - `strbuf_split()` functions). - -`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/pack-protocol.txt b/Documentation/technical/pack-protocol.txt index 462e20645f..4064fc796f 100644 --- a/Documentation/technical/pack-protocol.txt +++ b/Documentation/technical/pack-protocol.txt @@ -1,11 +1,11 @@ Packfile transfer protocols =========================== -Git supports transferring data in packfiles over the ssh://, git:// and +Git supports transferring data in packfiles over the ssh://, git://, http:// 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. +server to a client. The three transports (ssh, git, file) use the same +protocol to transfer data. http is documented in http-protocol.txt. 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; @@ -465,7 +465,7 @@ contain all the objects that the server will need to complete the new references. ---- - update-request = *shallow ( command-list | push-cert ) [pack-file] + update-request = *shallow ( command-list | push-cert ) [packfile] shallow = PKT-LINE("shallow" SP obj-id LF) @@ -491,7 +491,7 @@ references. *PKT-LINE(gpg-signature-lines LF) PKT-LINE("push-cert-end" LF) - pack-file = "PACK" 28*(OCTET) + packfile = "PACK" 28*(OCTET) ---- If the receiving end does not support delete-refs, the sending end MUST @@ -502,11 +502,11 @@ 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'. +The packfile 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, +A packfile 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 +case the client MUST send an empty packfile. 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. diff --git a/Documentation/technical/protocol-capabilities.txt b/Documentation/technical/protocol-capabilities.txt index 6d5424c1bd..4f8a7bfb4c 100644 --- a/Documentation/technical/protocol-capabilities.txt +++ b/Documentation/technical/protocol-capabilities.txt @@ -18,8 +18,9 @@ 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', 'quiet', and 'push-cert' capabilities -are sent and recognized by the receive-pack (push to server) process. +The 'atomic', '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 @@ -244,6 +245,14 @@ respond with the 'quiet' capability to suppress server-side progress reporting if the local progress reporting is also being suppressed (e.g., via `push -q`, or if stderr does not go to a tty). +atomic +------ + +If the server sends the 'atomic' capability it is capable of accepting +atomic pushes. If the pushing client requests this capability, the server +will update the refs in one atomic transaction. Either all refs are +updated or none. + allow-tip-sha1-in-want ---------------------- |