[RFC PATCH 1/3] git-merge: add option to format default message using multiple lines

From: i.Dark_Templar <darktemplar@dark-templar-archives.net>
Date: Feb 9, 2020, 13:16 UTC
Message-ID: <20200209131623.5827-2-darktemplar@dark-templar-archives.net>
In-Reply-To: <20200209131623.5827-1-darktemplar@dark-templar-archives.net>

If a lot of objects is merged at once, default commit message could become one very long line, which might be inconvenient to read. This change implements an option to change default autogenerated message so it'd take multiple lines, but each line wouldn't be long.

An artificial example.

Original merge commit message:
    Merge branch 'branch_with_some_long_name_1', remote-tracking branch 'clone/remote_branch_with_some_name', tags 'some_tag' and 'some_other_tag'; commit 'ae46a39cead2b42282abce725e90b561c06e94ba'; commit '33d0281e0eeb2a5e9907ebedc230e28c46865092' into merge7

Multiline merge commit message:
    Merge into merge8:
    branch 'branch_with_some_long_name_1'
    remote-tracking branch 'clone/remote_branch_with_some_name'
    tag 'some_tag'
    tag 'some_other_tag'
    commit 'ae46a39cead2b42282abce725e90b561c06e94ba'
    commit '33d0281e0eeb2a5e9907ebedc230e28c46865092'

Signed-off-by: i.Dark_Templar <darktemplar@dark-templar-archives.net>
---
 Documentation/config/fmt-merge-msg.txt |  6 +++
 builtin/fmt-merge-msg.c                | 66 +++++++++++++++++++++++++-
 2 files changed, 70 insertions(+), 2 deletions(-)

diff --git a/Documentation/config/fmt-merge-msg.txt b/Documentation/config/fmt-merge-msg.txt
index c73cfa90b7..8c12540fa7 100644
--- a/Documentation/config/fmt-merge-msg.txt
+++ b/Documentation/config/fmt-merge-msg.txt
@@ -8,3 +8,9 @@ merge.log::
 	most the specified number of one-line descriptions from the
 	actual commits that are being merged.  Defaults to false, and
 	true is a synonym for 20.
+
+merge.multilineMessage::
+	Make default merge commit message multiline. Every merged object
+	will be written using new line. This should ensure that
+	commit message wouldn't become one very long line when
+	there are a lot of merged objects.
diff --git a/builtin/fmt-merge-msg.c b/builtin/fmt-merge-msg.c
index 05a92c59d8..93d44b59d9 100644
--- a/builtin/fmt-merge-msg.c
+++ b/builtin/fmt-merge-msg.c
@@ -20,6 +20,7 @@ static const char * const fmt_merge_msg_usage[] = {
 };
 
 static int use_branch_desc;
+static int use_multiline_default_message = 0;
 
 int fmt_merge_msg_config(const char *key, const char *value, void *cb)
 {
@@ -32,6 +33,8 @@ int fmt_merge_msg_config(const char *key, const char *value, void *cb)
 			merge_log_config = DEFAULT_MERGE_LOG_LEN;
 	} else if (!strcmp(key, "merge.branchdesc")) {
 		use_branch_desc = git_config_bool(key, value);
+	} else if (!strcmp(key, "merge.multilinemessage")) {
+		use_multiline_default_message = git_config_bool(key, value);
 	} else {
 		return git_default_config(key, value, cb);
 	}
@@ -467,6 +470,61 @@ static void fmt_merge_msg_title(struct strbuf *out,
 		strbuf_addf(out, " into %s\n", current_branch);
 }
 
+static void fmt_merge_msg_title_multiline(struct strbuf *out,
+				const char *current_branch)
+{
+	int i = 0;
+	int j = 0;
+
+	if (!strcmp("master", current_branch))
+		strbuf_addstr(out, "Merge:\n");
+	else
+		strbuf_addf(out, "Merge into %s:\n", current_branch);
+
+	for (i = 0; i < srcs.nr; i++) {
+		struct src_data *src_data = srcs.items[i].util;
+		int add_origin = 0;
+
+		if (src_data->head_status == 1) {
+			strbuf_addf(out, "%s\n", srcs.items[i].string);
+			continue;
+		}
+
+		add_origin = strcmp(".", srcs.items[i].string);
+
+		if (src_data->head_status == 3) {
+			if (!add_origin)
+				strbuf_addstr(out, "HEAD\n");
+			else
+				strbuf_addf(out, "HEAD of %s\n", srcs.items[i].string);
+		}
+		for (j = 0; j < src_data->branch.nr; j++) {
+			if (!add_origin)
+				strbuf_addf(out, "branch %s\n", src_data->branch.items[j].string);
+			else
+				strbuf_addf(out, "branch %s of %s\n", src_data->branch.items[j].string, srcs.items[i].string);
+		}
+		for (j = 0; j < src_data->r_branch.nr; j++) {
+			if (!add_origin)
+				strbuf_addf(out, "remote-tracking branch %s\n", src_data->r_branch.items[j].string);
+			else
+				strbuf_addf(out, "remote-tracking branch %s of %s\n", src_data->r_branch.items[j].string, srcs.items[i].string);
+		}
+		for (j = 0; j < src_data->tag.nr; j++) {
+			if (!add_origin)
+				strbuf_addf(out, "tag %s\n", src_data->tag.items[j].string);
+			else
+				strbuf_addf(out, "tag %s of %s\n", src_data->tag.items[j].string, srcs.items[i].string);
+		}
+		for (j = 0; j < src_data->generic.nr; j++) {
+			if (!add_origin)
+				strbuf_addf(out, "commit %s\n", src_data->generic.items[j].string);
+			else
+				strbuf_addf(out, "commit %s of %s\n", src_data->generic.items[j].string, srcs.items[i].string);
+		}
+	}
+}
+
 static void fmt_tag_signature(struct strbuf *tagbuf,
 			      struct strbuf *sig,
 			      const char *buf,
@@ -634,8 +692,12 @@ int fmt_merge_msg(struct strbuf *in, struct strbuf *out,
 			die("error in line %d: %.*s", i, len, p);
 	}
 
-	if (opts->add_title && srcs.nr)
-		fmt_merge_msg_title(out, current_branch);
+	if (opts->add_title && srcs.nr) {
+		if (!use_multiline_default_message)
+			fmt_merge_msg_title(out, current_branch);
+		else
+			fmt_merge_msg_title_multiline(out, current_branch);
+	}
 
 	if (origins.nr)
 		fmt_merge_msg_sigs(out);

-- 
2.24.1