shortlog: add grouping option

In preparation for adding more grouping types, let's refactor the
committer/author grouping code and add a user-facing option that binds
them together. In particular:

  - the main option is now "--group", to make it clear
    that the various group types are mutually exclusive. The
    "--committer" option is an alias for "--group=committer".

  - we keep an enum rather than a binary flag, to prepare
    for more values

  - we prefer switch statements to ternary assignment, since
    other group types will need more custom code

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

4 files changed, 66 insertions, 13 deletions

diff --git a/Documentation/git-shortlog.txt b/Documentation/git-shortlog.txt
index a72ea7f7ba..6496d313c1 100644
--- a/Documentation/git-shortlog.txt
+++ b/Documentation/git-shortlog.txt
@@ -47,9 +47,16 @@ OPTIONS
 
 	Each pretty-printed commit will be rewrapped before it is shown.
 
+--group=<type>::
+	Group commits based on `<type>`. If no `--group` option is
+	specified, the default is `author`. `<type>` is one of:
++
+ - `author`, commits are grouped by author
+ - `committer`, commits are grouped by committer (the same as `-c`)
+
 -c::
 --committer::
-	Collect and show committer identities instead of authors.
+	This is an alias for `--group=committer`.
 
 -w[<width>[,<indent1>[,<indent2>]]]::
 	Linewrap the output by wrapping each line at `width`.  The first
diff --git a/builtin/shortlog.c b/builtin/shortlog.c
index edcf2e0d54..880ce19304 100644
--- a/builtin/shortlog.c
+++ b/builtin/shortlog.c
@@ -129,7 +129,17 @@ static void read_from_stdin(struct shortlog *log)
 	static const char *committer_match[2] = { "Commit: ", "committer " };
 	const char **match;
 
-	match = log->committer ? committer_match : author_match;
+	switch (log->group) {
+	case SHORTLOG_GROUP_AUTHOR:
+		match = author_match;
+		break;
+	case SHORTLOG_GROUP_COMMITTER:
+		match = committer_match;
+		break;
+	default:
+		BUG("unhandled shortlog group");
+	}
+
 	while (strbuf_getline_lf(&ident, stdin) != EOF) {
 		const char *v;
 		if (!skip_prefix(ident.buf, match[0], &v) &&
@@ -158,7 +168,7 @@ void shortlog_add_commit(struct shortlog *log, struct commit *commit)
 	struct strbuf ident = STRBUF_INIT;
 	struct strbuf oneline = STRBUF_INIT;
 	struct pretty_print_context ctx = {0};
-	const char *fmt;
+	const char *oneline_str;
 
 	ctx.fmt = CMIT_FMT_USERFORMAT;
 	ctx.abbrev = log->abbrev;
@@ -166,19 +176,28 @@ void shortlog_add_commit(struct shortlog *log, struct commit *commit)
 	ctx.date_mode.type = DATE_NORMAL;
 	ctx.output_encoding = get_log_output_encoding();
 
-	fmt = log->committer ?
-		(log->email ? "%cN <%cE>" : "%cN") :
-		(log->email ? "%aN <%aE>" : "%aN");
-
-	format_commit_message(commit, fmt, &ident, &ctx);
 	if (!log->summary) {
 		if (log->user_format)
 			pretty_print_commit(&ctx, commit, &oneline);
 		else
 			format_commit_message(commit, "%s", &oneline, &ctx);
 	}
-
-	insert_one_record(log, ident.buf, oneline.len ? oneline.buf : "<none>");
+	oneline_str = oneline.len ? oneline.buf : "<none>";
+
+	switch (log->group) {
+	case SHORTLOG_GROUP_AUTHOR:
+		format_commit_message(commit,
+				      log->email ? "%aN <%aE>" : "%aN",
+				      &ident, &ctx);
+		insert_one_record(log, ident.buf, oneline_str);
+		break;
+	case SHORTLOG_GROUP_COMMITTER:
+		format_commit_message(commit,
+				      log->email ? "%cN <%cE>" : "%cN",
+				      &ident, &ctx);
+		insert_one_record(log, ident.buf, oneline_str);
+		break;
+	}
 
 	strbuf_release(&ident);
 	strbuf_release(&oneline);
@@ -241,6 +260,21 @@ static int parse_wrap_args(const struct option *opt, const char *arg, int unset)
 	return 0;
 }
 
+static int parse_group_option(const struct option *opt, const char *arg, int unset)
+{
+	struct shortlog *log = opt->value;
+
+	if (unset || !strcasecmp(arg, "author"))
+		log->group = SHORTLOG_GROUP_AUTHOR;
+	else if (!strcasecmp(arg, "committer"))
+		log->group = SHORTLOG_GROUP_COMMITTER;
+	else
+		return error(_("unknown group type: %s"), arg);
+
+	return 0;
+}
+
+
 void shortlog_init(struct shortlog *log)
 {
 	memset(log, 0, sizeof(*log));
@@ -260,8 +294,9 @@ int cmd_shortlog(int argc, const char **argv, const char *prefix)
 	int nongit = !startup_info->have_repository;
 
 	const struct option options[] = {
-		OPT_BOOL('c', "committer", &log.committer,
-			 N_("Group by committer rather than author")),
+		OPT_SET_INT('c', "committer", &log.group,
+			    N_("Group by committer rather than author"),
+			    SHORTLOG_GROUP_COMMITTER),
 		OPT_BOOL('n', "numbered", &log.sort_by_number,
 			 N_("sort output according to the number of commits per author")),
 		OPT_BOOL('s', "summary", &log.summary,
@@ -271,6 +306,8 @@ int cmd_shortlog(int argc, const char **argv, const char *prefix)
 		OPT_CALLBACK_F('w', NULL, &log, N_("<w>[,<i1>[,<i2>]]"),
 			N_("Linewrap output"), PARSE_OPT_OPTARG,
 			&parse_wrap_args),
+		OPT_CALLBACK(0, "group", &log, N_("field"),
+			N_("Group by field"), parse_group_option),
 		OPT_END(),
 	};
 
diff --git a/shortlog.h b/shortlog.h
index 2fa61c4294..876a52158d 100644
--- a/shortlog.h
+++ b/shortlog.h
@@ -15,7 +15,11 @@ struct shortlog {
 	int in2;
 	int user_format;
 	int abbrev;
-	int committer;
+
+	enum {
+		SHORTLOG_GROUP_AUTHOR = 0,
+		SHORTLOG_GROUP_COMMITTER,
+	} group;
 
 	char *common_repo_prefix;
 	int email;
diff --git a/t/t4201-shortlog.sh b/t/t4201-shortlog.sh
index d3a7ce6bbb..65e4468746 100755
--- a/t/t4201-shortlog.sh
+++ b/t/t4201-shortlog.sh
@@ -215,4 +215,9 @@ test_expect_success 'shortlog --committer (external)' '
 	test_cmp expect actual
 '
 
+test_expect_success '--group=committer is the same as --committer' '
+	git shortlog -ns --group=committer HEAD >actual &&
+	test_cmp expect actual
+'
+
 test_done