[PATCH 2/2] rebase: allow overriding the maximal length of the generated labels

["Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>]

From: Johannes Schindelin <johannes.schindelin@gmx.de>

With this change, users can override the compiled-in default for the
maximal length of the label names generated by `git rebase
--rebase-merges`.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Mark Ruvald Pedersen <mped@demant.com>
---
 Documentation/config/rebase.txt |  6 ++++++
 sequencer.c                     |  8 ++++++--
 t/t3430-rebase-merges.sh        | 11 +++++++++++
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/Documentation/config/rebase.txt b/Documentation/config/rebase.txt
index afaf6dad99b..9c248accec2 100644
--- a/Documentation/config/rebase.txt
+++ b/Documentation/config/rebase.txt
@@ -77,3 +77,9 @@ rebase.rebaseMerges::
 	equivalent to `--no-rebase-merges`. Passing `--rebase-merges` on the
 	command line, with or without an argument, overrides any
 	`rebase.rebaseMerges` configuration.
+
+rebase.maxLabelLength::
+	When generating label names from commit subjects, truncate the names to
+	this length. By default, the names are truncated to a little less than
+	`NAME_MAX` (to allow e.g. `.lock` files to be written for the
+	corresponding loose refs).
diff --git a/sequencer.c b/sequencer.c
index be837bd2948..b1fc44f0321 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -5349,6 +5349,7 @@ struct label_state {
 	struct oidmap commit2label;
 	struct hashmap labels;
 	struct strbuf buf;
+	int max_label_length;
 };
 
 static const char *label_oid(struct object_id *oid, const char *label,
@@ -5406,7 +5407,7 @@ static const char *label_oid(struct object_id *oid, const char *label,
 	} else {
 		struct strbuf *buf = &state->buf;
 		int label_is_utf8 = 1; /* start with this assumption */
-		size_t max_len = buf->len + GIT_MAX_LABEL_LENGTH;
+		size_t max_len = buf->len + state->max_label_length;
 
 		/*
 		 * Sanitize labels by replacing non-alpha-numeric characters
@@ -5504,7 +5505,8 @@ static int make_script_with_merges(struct pretty_print_context *pp,
 	struct string_entry *entry;
 	struct oidset interesting = OIDSET_INIT, child_seen = OIDSET_INIT,
 		shown = OIDSET_INIT;
-	struct label_state state = { OIDMAP_INIT, { NULL }, STRBUF_INIT };
+	struct label_state state =
+		{ OIDMAP_INIT, { NULL }, STRBUF_INIT, GIT_MAX_LABEL_LENGTH };
 
 	int abbr = flags & TODO_LIST_ABBREVIATE_CMDS;
 	const char *cmd_pick = abbr ? "p" : "pick",
@@ -5512,6 +5514,8 @@ static int make_script_with_merges(struct pretty_print_context *pp,
 		*cmd_reset = abbr ? "t" : "reset",
 		*cmd_merge = abbr ? "m" : "merge";
 
+	git_config_get_int("rebase.maxlabellength", &state.max_label_length);
+
 	oidmap_init(&commit2todo, 0);
 	oidmap_init(&state.commit2label, 0);
 	hashmap_init(&state.labels, labels_cmp, NULL, 0);
diff --git a/t/t3430-rebase-merges.sh b/t/t3430-rebase-merges.sh
index 96ae0edf1e1..ac5c390652f 100755
--- a/t/t3430-rebase-merges.sh
+++ b/t/t3430-rebase-merges.sh
@@ -586,4 +586,15 @@ test_expect_success 'progress shows the correct total' '
 	test_line_count = 14 progress
 '
 
+test_expect_success 'truncate label names' '
+	commit=$(git commit-tree -p HEAD^ -p HEAD -m "0123456789 我 123" HEAD^{tree}) &&
+	git merge --ff-only $commit &&
+
+	done="$(git rev-parse --git-path rebase-merge/done)" &&
+	git -c rebase.maxLabelLength=14 rebase --rebase-merges -x "cp \"$done\" out" --root &&
+	grep "label 0123456789-我$" out &&
+	git -c rebase.maxLabelLength=13 rebase --rebase-merges -x "cp \"$done\" out" --root &&
+	grep "label 0123456789-$" out
+'
+
 test_done
-- 
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