diff options
Diffstat (limited to 'Documentation/technical')
| -rw-r--r-- | Documentation/technical/api-argv-array.txt | 3 | ||||
| -rw-r--r-- | Documentation/technical/api-lockfile.txt | 220 | ||||
| -rw-r--r-- | Documentation/technical/api-parse-options.txt | 19 | ||||
| -rw-r--r-- | Documentation/technical/api-submodule-config.txt | 62 | ||||
| -rw-r--r-- | Documentation/technical/index-format.txt | 2 | ||||
| -rw-r--r-- | Documentation/technical/pack-protocol.txt | 46 | ||||
| -rw-r--r-- | Documentation/technical/protocol-common.txt | 5 | ||||
| -rw-r--r-- | Documentation/technical/racy-git.txt | 8 |
8 files changed, 121 insertions, 244 deletions
diff --git a/Documentation/technical/api-argv-array.txt b/Documentation/technical/api-argv-array.txt index 1a79781..8076172 100644 --- a/Documentation/technical/api-argv-array.txt +++ b/Documentation/technical/api-argv-array.txt @@ -46,6 +46,9 @@ Functions Format a string and push it onto the end of the array. This is a convenience wrapper combining `strbuf_addf` and `argv_array_push`. +`argv_array_pushv`:: + Push a null-terminated array of strings onto the end of the array. + `argv_array_pop`:: Remove the final element from the array. If there are no elements in the array, do nothing. diff --git a/Documentation/technical/api-lockfile.txt b/Documentation/technical/api-lockfile.txt deleted file mode 100644 index 93b5f23..0000000 --- a/Documentation/technical/api-lockfile.txt +++ /dev/null @@ -1,220 +0,0 @@ -lockfile API -============ - -The lockfile API serves two purposes: - -* 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 -------------- - -hold_lock_file_for_update:: - - 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` 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` 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` 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 1f2db31..5f0757d 100644 --- a/Documentation/technical/api-parse-options.txt +++ b/Documentation/technical/api-parse-options.txt @@ -168,6 +168,12 @@ There are some macros to easily define options: Introduce an option with integer argument. The integer is put into `int_var`. +`OPT_MAGNITUDE(short, long, &unsigned_long_var, description)`:: + Introduce an option with a size argument. The argument must be a + non-negative integer and may include a suffix of 'k', 'm' or 'g' to + scale the provided value by 1024, 1024^2 or 1024^3 respectively. + The scaled value is put into `unsigned_long_var`. + `OPT_DATE(short, long, &int_var, description)`:: Introduce an option with date argument, see `approxidate()`. The timestamp is put into `int_var`. @@ -212,6 +218,19 @@ There are some macros to easily define options: Use it to hide deprecated options that are still to be recognized and ignored silently. +`OPT_PASSTHRU(short, long, &char_var, arg_str, description, flags)`:: + Introduce an option that will be reconstructed into a char* string, + which must be initialized to NULL. This is useful when you need to + pass the command-line option to another command. Any previous value + will be overwritten, so this should only be used for options where + the last one specified on the command line wins. + +`OPT_PASSTHRU_ARGV(short, long, &argv_array_var, arg_str, description, flags)`:: + Introduce an option where all instances of it on the command-line will + be reconstructed into an argv_array. This is useful when you need to + pass the command-line option, which can be specified multiple times, + to another command. + The last element of the array must be `OPT_END()`. diff --git a/Documentation/technical/api-submodule-config.txt b/Documentation/technical/api-submodule-config.txt new file mode 100644 index 0000000..941fa17 --- /dev/null +++ b/Documentation/technical/api-submodule-config.txt @@ -0,0 +1,62 @@ +submodule config cache API +========================== + +The submodule config cache API allows to read submodule +configurations/information from specified revisions. Internally +information is lazily read into a cache that is used to avoid +unnecessary parsing of the same .gitmodule files. Lookups can be done by +submodule path or name. + +Usage +----- + +To initialize the cache with configurations from the worktree the caller +typically first calls `gitmodules_config()` to read values from the +worktree .gitmodules and then to overlay the local git config values +`parse_submodule_config_option()` from the config parsing +infrastructure. + +The caller can look up information about submodules by using the +`submodule_from_path()` or `submodule_from_name()` functions. They return +a `struct submodule` which contains the values. The API automatically +initializes and allocates the needed infrastructure on-demand. If the +caller does only want to lookup values from revisions the initialization +can be skipped. + +If the internal cache might grow too big or when the caller is done with +the API, all internally cached values can be freed with submodule_free(). + +Data Structures +--------------- + +`struct submodule`:: + + This structure is used to return the information about one + submodule for a certain revision. It is returned by the lookup + functions. + +Functions +--------- + +`void submodule_free()`:: + + Use these to free the internally cached values. + +`int parse_submodule_config_option(const char *var, const char *value)`:: + + Can be passed to the config parsing infrastructure to parse + local (worktree) submodule configurations. + +`const struct submodule *submodule_from_path(const unsigned char *commit_sha1, const char *path)`:: + + Lookup values for one submodule by its commit_sha1 and path. + +`const struct submodule *submodule_from_name(const unsigned char *commit_sha1, const char *name)`:: + + The same as above but lookup by name. + +If given the null_sha1 as commit_sha1 the local configuration of a +submodule will be returned (e.g. consolidated values from local git +configuration and the .gitmodules file in the worktree). + +For an example usage see test-submodule-config.c. diff --git a/Documentation/technical/index-format.txt b/Documentation/technical/index-format.txt index b7093af..7392ff6 100644 --- a/Documentation/technical/index-format.txt +++ b/Documentation/technical/index-format.txt @@ -275,7 +275,7 @@ Git index format - The directory name terminated by NUL. - - A number of untrached file/dir names terminated by NUL. + - A number of untracked file/dir names terminated by NUL. The remaining data of each directory block is grouped by type: diff --git a/Documentation/technical/pack-protocol.txt b/Documentation/technical/pack-protocol.txt index 4064fc7..c6977bb 100644 --- a/Documentation/technical/pack-protocol.txt +++ b/Documentation/technical/pack-protocol.txt @@ -14,6 +14,14 @@ 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. +pkt-line Format +--------------- + +The descriptions below build on the pkt-line format described in +protocol-common.txt. When the grammar indicate `PKT-LINE(...)`, unless +otherwise noted the usual pkt-line LF rules apply: the sender SHOULD +include a LF, but the receiver MUST NOT complain if it is not present. + Transports ---------- There are three transports over which the packfile protocol is @@ -143,9 +151,6 @@ with the object name that each reference currently points to. 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. @@ -165,15 +170,15 @@ MUST peel the ref if it's an annotated tag. flush-pkt no-refs = PKT-LINE(zero-id SP "capabilities^{}" - NUL capability-list LF) + NUL capability-list) list-of-refs = first-ref *other-ref first-ref = PKT-LINE(obj-id SP refname - NUL capability-list LF) + NUL capability-list) other-ref = PKT-LINE(other-tip / other-peeled) - other-tip = obj-id SP refname LF - other-peeled = obj-id SP refname "^{}" LF + other-tip = obj-id SP refname + other-peeled = obj-id SP refname "^{}" shallow = PKT-LINE("shallow" SP obj-id) @@ -216,8 +221,8 @@ out of what the server said it could do with the first 'want' line. 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) + first-want = PKT-LINE("want" SP obj-id SP capability-list) + additional-want = PKT-LINE("want" SP obj-id) depth = 1*DIGIT ---- @@ -284,7 +289,7 @@ so that there is always a block of 32 "in-flight on the wire" at a time. compute-end have-list = *have-line - have-line = PKT-LINE("have" SP obj-id LF) + have-line = PKT-LINE("have" SP obj-id) compute-end = flush-pkt / PKT-LINE("done") ---- @@ -348,10 +353,10 @@ 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_multi = PKT-LINE("ACK" SP obj-id ack_status) ack_status = "continue" / "common" / "ready" - ack = PKT-LINE("ACK SP obj-id LF) - nak = PKT-LINE("NAK" LF) + ack = PKT-LINE("ACK" SP obj-id) + nak = PKT-LINE("NAK") ---- A simple clone may look like this (with no 'have' lines): @@ -467,10 +472,10 @@ references. ---- update-request = *shallow ( command-list | push-cert ) [packfile] - shallow = PKT-LINE("shallow" SP obj-id LF) + shallow = PKT-LINE("shallow" SP obj-id) - command-list = PKT-LINE(command NUL capability-list LF) - *PKT-LINE(command LF) + command-list = PKT-LINE(command NUL capability-list) + *PKT-LINE(command) flush-pkt command = create / delete / update @@ -521,7 +526,8 @@ 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. +line. Note that the the trailing LF in push-cert PKT-LINEs is _not_ +optional; it must be present. Currently, the following header fields are defined: @@ -560,12 +566,12 @@ update was successful, or 'ng [refname] [error]' if the update was not. 1*(command-status) flush-pkt - unpack-status = PKT-LINE("unpack" SP unpack-result LF) + unpack-status = PKT-LINE("unpack" SP unpack-result) 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) + command-ok = PKT-LINE("ok" SP refname) + command-fail = PKT-LINE("ng" SP refname SP error-msg) error-msg = 1*(OCTECT) ; where not "ok" ---- diff --git a/Documentation/technical/protocol-common.txt b/Documentation/technical/protocol-common.txt index 889985f..bf30167 100644 --- a/Documentation/technical/protocol-common.txt +++ b/Documentation/technical/protocol-common.txt @@ -62,7 +62,10 @@ 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. +MUST be included in the total length. Receivers MUST treat pkt-lines +with non-binary data the same whether or not they contain the trailing +LF (stripping the LF if present, and not complaining when it is +missing). The maximum length of a pkt-line's data component is 65520 bytes. Implementations MUST NOT send pkt-line whose length exceeds 65524 diff --git a/Documentation/technical/racy-git.txt b/Documentation/technical/racy-git.txt index 242a044..4a8be4d 100644 --- a/Documentation/technical/racy-git.txt +++ b/Documentation/technical/racy-git.txt @@ -41,13 +41,17 @@ With a `USE_STDEV` compile-time option, `st_dev` is also 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 +members are also compared. On Linux, this is not enabled by default 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 granularity with filesystems, -2005-01-04). +2005-01-04). This patch is included in kernel 2.6.11 and newer, but +only fixes the issue for file systems with exactly 1 ns or 1 s +resolution. Other file systems are still broken in current Linux +kernels (e.g. CEPH, CIFS, NTFS, UDF), see +https://lkml.org/lkml/2015/6/9/714 Racy Git -------- |