lockfile.c: introduce 'hold_lock_file_for_update_mode'

We use 'hold_lock_file_for_update' (and the '_timeout') variant to
acquire a lock when updating references, the commit-graph file, and so
on.

In particular, the commit-graph machinery uses this to acquire a
temporary file that is used to write a non-split commit-graph. In a
subsequent commit, an issue in the commit-graph machinery produces
graph files that have a different permission based on whether or not
they are part of a multi-layer graph will be addressed.

To do so, the commit-graph machinery will need a version of
'hold_lock_file_for_update' that takes the permission bits from the
caller.

Introduce such a function in this patch for both the
'hold_lock_file_for_update' and 'hold_lock_file_for_update_timeout'
functions, and leave the existing functions alone by inlining their
definitions in terms of the new mode variants.

Note that, like in the previous commit, 'hold_lock_file_for_update_mode'
is not guarenteed to set the given mode, since it may be modified by
both the umask and 'core.sharedRepository'.

Note also that even though the commit-graph machinery only calls
'hold_lock_file_for_update', that this is defined in terms of
'hold_lock_file_for_update_timeout', and so both need an additional mode
parameter here.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 28 insertions, 4 deletions

diff --git a/lockfile.h b/lockfile.h
index 9843053..db93e6b 100644
--- a/lockfile.h
+++ b/lockfile.h
@@ -90,6 +90,15 @@
  * functions. In particular, the state diagram and the cleanup
  * machinery are all implemented in the tempfile module.
  *
+ * Permission bits
+ * ---------------
+ *
+ * If you call either `hold_lock_file_for_update_mode` or
+ * `hold_lock_file_for_update_timeout_mode`, you can specify a suggested
+ * mode for the underlying temporary file. Note that the file isn't
+ * guaranteed to have this exact mode, since it may be limited by either
+ * the umask, 'core.sharedRepository', or both. See `adjust_shared_perm`
+ * for more.
  *
  * Error handling
  * --------------
@@ -156,12 +165,20 @@ struct lock_file {
  * file descriptor for writing to it, or -1 on error. If the file is
  * currently locked, retry with quadratic backoff for at least
  * timeout_ms milliseconds. If timeout_ms is 0, try exactly once; if
- * timeout_ms is -1, retry indefinitely. The flags argument and error
- * handling are described above.
+ * timeout_ms is -1, retry indefinitely. The flags argument, error
+ * handling, and mode are described above.
  */
-int hold_lock_file_for_update_timeout(
+int hold_lock_file_for_update_timeout_mode(
+		struct lock_file *lk, const char *path,
+		int flags, long timeout_ms, int mode);
+
+static inline int hold_lock_file_for_update_timeout(
 		struct lock_file *lk, const char *path,
-		int flags, long timeout_ms);
+		int flags, long timeout_ms)
+{
+	return hold_lock_file_for_update_timeout_mode(lk, path, flags,
+						      timeout_ms, 0666);
+}
 
 /*
  * Attempt to create a lockfile for the file at `path` and return a
@@ -175,6 +192,13 @@ static inline int hold_lock_file_for_update(
 	return hold_lock_file_for_update_timeout(lk, path, flags, 0);
 }
 
+static inline int hold_lock_file_for_update_mode(
+		struct lock_file *lk, const char *path,
+		int flags, int mode)
+{
+	return hold_lock_file_for_update_timeout_mode(lk, path, flags, 0, mode);
+}
+
 /*
  * Return a nonzero value iff `lk` is currently locked.
  */