read_cache: roll back lock in update_index_if_able()

Martin Ågren · gitster · commit b74c90fb419b · 2017-10-07T10:20:56.000+09:00
`update_index_if_able()` used to always commit the lock or roll it back. Commit 03b8664 (read-cache: new API write_locked_index instead of write_index/write_cache, 2014-06-13) stopped rolling it back in case a write was not even attempted. This change in behavior is not motivated in the commit message and appears to be accidental: the `else`-path was removed, although that changed the behavior in case the `if` shortcuts. Reintroduce the rollback and document this behavior. While at it, move the documentation on this function from the function definition to the function declaration in cache.h. If `write_locked_index(..., COMMIT_LOCK)` fails, it will roll back the lock for us (see the previous commit). Noticed-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Martin Ågren <martin.agren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/cache.h b/cache.h
@@ -734,6 +734,10 @@ extern void fill_stat_cache_info(struct cache_entry *ce, struct stat *st);
 extern int refresh_index(struct index_state *, unsigned int flags, const struct pathspec *pathspec, char *seen, const char *header_msg);
 extern struct cache_entry *refresh_cache_entry(struct cache_entry *, unsigned int);
 
+/*
+ * Opportunistically update the index but do not complain if we can't.
+ * The lockfile is always committed or rolled back.
+ */
 extern void update_index_if_able(struct index_state *, struct lock_file *);
 
 extern int hold_locked_index(struct lock_file *, int);
diff --git a/read-cache.c b/read-cache.c
@@ -2176,14 +2176,13 @@ static int has_racy_timestamp(struct index_state *istate)
 	return 0;
 }
 
-/*
- * Opportunistically update the index but do not complain if we can't
- */
 void update_index_if_able(struct index_state *istate, struct lock_file *lockfile)
 {
 	if ((istate->cache_changed || has_racy_timestamp(istate)) &&
 	    verify_index(istate))
 		write_locked_index(istate, lockfile, COMMIT_LOCK);
+	else
+		rollback_lock_file(lockfile);
 }
 
 /*

Original file line number	Diff line number	Diff line change
`@@ -2176,14 +2176,13 @@ static int has_racy_timestamp(struct index_state *istate)`
`2176`	`2176`	`return 0;`
`2177`	`2177`	`}`
`2178`	`2178`
`2179`		`-/*`
`2180`		`- * Opportunistically update the index but do not complain if we can't`
`2181`		`- */`
`2182`	`2179`	`void update_index_if_able(struct index_state istate, struct lock_file lockfile)`
`2183`	`2180`	`{`
`2184`	`2181`	`if ((istate->cache_changed \|\| has_racy_timestamp(istate)) &&`
`2185`	`2182`	`verify_index(istate))`
`2186`	`2183`	`write_locked_index(istate, lockfile, COMMIT_LOCK);`
	`2184`	`+ else`
	`2185`	`+ rollback_lock_file(lockfile);`
`2187`	`2186`	`}`
`2188`	`2187`
`2189`	`2188`	`/*`