rebase: allow overriding the maximal length of the generated labels

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>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/sequencer.c b/sequencer.c
index c3e23a9..5b9b81e 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -5339,6 +5339,7 @@ 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,
@@ -5396,7 +5397,7 @@ 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
@@ -5494,7 +5495,8 @@ 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",
@@ -5502,6 +5504,8 @@ 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);