[PATCH] describe: Refresh the index when run with --dirty

[Allan Caffee <allan.caffee@gmail.com>]

When running git describe --dirty the index should be refreshed.  Previously
the cached index would cause describe to think that the index was dirty when,
in reality, it was just stale.

The issue was exposed by python setuptools which hardlinks files into another
directory when building a distribution.
---
 builtin/describe.c |   14 ++++++++++++--
 1 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/builtin/describe.c b/builtin/describe.c
index 66fc291..792af76 100644
--- a/builtin/describe.c
+++ b/builtin/describe.c
@@ -24,6 +24,7 @@ static int longformat;
 static int abbrev = -1; /* unspecified */
 static int max_candidates = 10;
 static struct hash_table names;
+static struct lock_file index_lock; /* real index */
 static int have_util;
 static const char *pattern;
 static int always;
@@ -399,6 +400,7 @@ static void describe(const char *arg, int last_one)
 int cmd_describe(int argc, const char **argv, const char *prefix)
 {
 	int contains = 0;
+	int fd;
 	struct option options[] = {
 		OPT_BOOLEAN(0, "contains",   &contains, "find the tag that comes after the commit"),
 		OPT_BOOLEAN(0, "debug",      &debug, "debug search strategy on stderr"),
@@ -462,8 +464,16 @@ int cmd_describe(int argc, const char **argv, const char *prefix)
 		die(_("No names found, cannot describe anything."));
 
 	if (argc == 0) {
-		if (dirty && !cmd_diff_index(ARRAY_SIZE(diff_index_args) - 1, diff_index_args, prefix))
-			dirty = NULL;
+		if (dirty) {
+			read_cache();
+			refresh_index(&the_index, REFRESH_QUIET|REFRESH_UNMERGED, NULL, NULL, NULL);
+			fd = hold_locked_index(&index_lock, 0);
+			if (0 <= fd)
+				update_index_if_able(&the_index, &index_lock);
+
+			if (!cmd_diff_index(ARRAY_SIZE(diff_index_args) - 1, diff_index_args, prefix))
+				dirty = NULL;
+		}
 		describe("HEAD", 1);
 	} else if (dirty) {
 		die(_("--dirty is incompatible with committishes"));
-- 
1.7.3.2