git-log-describe.awk: allow limiting to cache

The `--contains` option (default, enabled via `-vfast=0`) does not
show a result if there is no tag following a commit. The `-vcache_only`
option prevents execution of `git describe` and thereby speeds up
post-processing.

1 files changed, 6 insertions, 1 deletions

diff --git a/git-log-describe.awk b/git-log-describe.awk
index a491e13..74d8e42 100755
--- a/git-log-describe.awk
+++ b/git-log-describe.awk
@@ -10,6 +10,8 @@
 # -vcache_dir=DIR       Use DIR to store cached git-describe results. DIR will
 #                       be created if non-existent. Implies -vcache=1.
 # -vcache_ro={0|1}      Set to 1 to prevent creating new files in cache.
+# -vcache_only={0|1}    Set to 1 to use only cache entries, do not execute
+#                       git-describe for missing entries. Implies -vcache_ro=1.
 # -vfast={0|1}          If 0 (default), then --contains will be used which
 #                       relates to the first tag containing this commit.
 #                       Otherwise, --first-parent will be used which relates to
@@ -42,6 +44,9 @@ BEGIN {
 		if (cache_dir) cache_dir = cache_dir "/contains";
 	}
 
+	# If git-describe is disabled, then the cache is effectively read-only.
+	if (cache_only) cache_ro = 1;
+
 	if (cache_dir) {
 		# Skip cache directory if non-existent and read only or if the
 		# directory cannot be created.
@@ -120,7 +125,7 @@ function git_describe(hash) {
 	}
 
 	# cache entry was unavailable, get a description now.
-	if (!desc) {
+	if (!desc && !cache_only) {
 		cmd = "git describe " opts " " hash " 2>/dev/null";
 		cmd | getline desc;
 		close(cmd);