merge: Make 'merge.log' an integer or boolean option

Make 'merge.log' an integer or boolean option to set the number of
shortlog entries to display in the merge commit. Note that it defaults
to false, and that true means a default value of 20. Also update
corresponding documentation.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Thanks-to: Jonathan Nieder <jrnieder@gmail.com>
Thanks-to: Johannes Sixt <j.sixt@viscovery.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-fmt-merge-msg.txt

@@ -54,8 +54,10 @@ CONFIGURATION
 -------------
 
 merge.log::
-	Whether to include summaries of merged commits in newly
-	merge commit messages. False by default.
+	In addition to branch names, populate the log message with at
+	most the specified number of one-line descriptions from the
+	actual commits that are being merged.  Defaults to false, and
+	true is a synoym for 20.
 
 merge.summary::
 	Synonym to `merge.log`; this is deprecated and will be removed in

Documentation/merge-config.txt

@@ -7,8 +7,10 @@ merge.conflictstyle::
 	marker and the original text before the `=======` marker.
 
 merge.log::
-	Whether to include summaries of merged commits in newly created
-	merge commit messages. False by default.
+	In addition to branch names, populate the log message with at
+	most the specified number of one-line descriptions from the
+	actual commits that are being merged.  Defaults to false, and
+	true is a synoym for 20.
 
 merge.renameLimit::
 	The number of files to consider when performing rename detection

builtin/fmt-merge-msg.c

@@ -15,15 +15,13 @@ static int shortlog_len;
 
 static int fmt_merge_msg_config(const char *key, const char *value, void *cb)
 {
-	static int found_merge_log = 0;
-	if (!strcmp("merge.log", key)) {
-		found_merge_log = 1;
-		shortlog_len = git_config_bool(key, value) ? DEFAULT_MERGE_LOG_LEN : 0;
-		return 0;
-	}
-	if (!found_merge_log && !strcmp("merge.summary", key)) {
-		shortlog_len = git_config_bool(key, value) ? DEFAULT_MERGE_LOG_LEN : 0;
-		return 0;
+	if (!strcmp(key, "merge.log") || !strcmp(key, "merge.summary")) {
+		int is_bool;
+		shortlog_len = git_config_bool_or_int(key, value, &is_bool);
+		if (!is_bool && shortlog_len < 0)
+			return error("%s: negative length %s", key, value);
+		if (is_bool && shortlog_len)
+			shortlog_len = DEFAULT_MERGE_LOG_LEN;
 	}
 	return 0;
 }

builtin/merge.c

@@ -503,7 +503,12 @@ static int git_merge_config(const char *k, const char *v, void *cb)
 	else if (!strcmp(k, "pull.octopus"))
 		return git_config_string(&pull_octopus, k, v);
 	else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary")) {
-		shortlog_len = git_config_bool(k, v) ? DEFAULT_MERGE_LOG_LEN : 0;
+		int is_bool;
+		shortlog_len = git_config_bool_or_int(k, v, &is_bool);
+		if (!is_bool && shortlog_len < 0)
+			return error("%s: negative length %s", k, v);
+		if (is_bool && shortlog_len)
+			shortlog_len = DEFAULT_MERGE_LOG_LEN;
 		return 0;
 	}
 	return git_diff_ui_config(k, v, cb);