git-log-describe: describe first tag following a commit

Instead of showing where a commit was derived from, use `--contains` to
show a description relative to a tag containing the commit.

1 files changed, 12 insertions, 3 deletions

diff --git a/git-log-describe.awk b/git-log-describe.awk
index 27063c4..c0ab37e 100755
--- a/git-log-describe.awk
+++ b/git-log-describe.awk
@@ -1,6 +1,8 @@
 #!/usr/bin/awk -f
-# Adds a "git describe" (nearest tag) output for `git log` (with support for
-# color escapes and --graph markers). --oneline is not supported.
+# Adds the first tag containing a commit for each git-log entry.
+# `git log --color` and `git log --graph` are supported.  --oneline is not
+# supported (yet).
+# If there is no tag after the commit, no description is shown.
 #
 # Optional variables:
 # -vcache={0|1}         Enable a cache for git describe outputs. If set to 1,
@@ -9,6 +11,10 @@
 #                       be created if non-existent. Implies -vcache=1.
 # -vcache_ro={0|1}      Set to 1 to prevent creating new files in cache.
 #
+# NOTE: when cache is enabled, one must clear it when the `git describe` options
+# are changed (see variable "opts" below) or when a new tag is added before an
+# existing tag.
+#
 # Copyright (c) 2013 Peter Wu <lekensteyn@gmail.com>
 # Licensed under GPLv3 or any latter version
 
@@ -26,6 +32,9 @@ BEGIN {
 		if (cache_ro && !is_dir(cache_dir) || !mkdir_p(cache_dir))
 			cache_dir = "";
 	}
+
+	# Use `git-describe --contains` to show which tag contains this commit.
+	opts = "--contains";
 }
 
 { print; }
@@ -97,7 +106,7 @@ function git_describe(hash) {
 
 	# cache entry was unavailable, get a description now.
 	if (!desc) {
-		"git describe --first-parent " hash | getline desc;
+		"git describe " opts " " hash " 2>/dev/null" | getline desc;
 
 		# write description to cache if allowed.
 		if (cache_dir && desc && !cache_ro) {