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 writing to the file
- descriptor returned by those functions (also available via
- `lock->fd`).
+* 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`.
+ 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`,
- `rollback_lock_file`, or `reopen_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
`hold_lock_file_for_append`.
If the program exits before you have called one of `commit_lock_file`,
-`rollback_lock_file`, or `close_lock_file`, an `atexit(3)` handler
-will close and remove the lockfile, rolling back any uncommitted
-changes.
+`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)` yourself!
-Otherwise the `struct lock_file` structure would still think that the
-file descriptor needs to be closed, and a later call to
-`commit_lock_file` or `rollback_lock_file` or program exit would
-result in duplicate calls to `close(2)`. Worse yet, if you `close(2)`
+`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 call to `commit_lock_file` or `rollback_lock_file`
-might close that unrelated file descriptor.
+purpose, then a commit or rollback might close that unrelated file
+descriptor.
Error handling
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_NODEREF::
+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_NODEREF` is set, then the lockfile is created
+ 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
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
+ `hold_lock_file_for_append`, close the file descriptor, and
rename the lockfile to its final destination. Return 0 upon
- success or a negative value on failure 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.
+ 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.
+ 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`, and close the file descriptor.
- Return 0 upon success. On failure to `close(2)`, return a
- negative value and rollback the lock file. Usually
- `commit_lock_file` or `rollback_lock_file` should eventually
- be called if `close_lock_file` succeeds.
+ `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::