merge-tree.c: allow specifying the merge-base when --stdin is passed

The previous commit added a `--merge-base` option in order to allow
using a specified merge-base for the merge.  Extend the input accepted
by `--stdin` to also allow a specified merge-base with each merge
requested.  For example:

    printf "<b3> -- <b1> <b2>" | git merge-tree --stdin

does a merge of b1 and b2, and uses b3 as the merge-base.

Signed-off-by: Kyle Zhao <kylezhao@tencent.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>

1 files changed, 19 insertions, 2 deletions

diff --git a/builtin/merge-tree.c b/builtin/merge-tree.c
index 62c6d43cdb..330f779e8b 100644
--- a/builtin/merge-tree.c
+++ b/builtin/merge-tree.c
@@ -557,12 +557,29 @@ int cmd_merge_tree(int argc, const char **argv, const char *prefix)
 		while (strbuf_getline_lf(&buf, stdin) != EOF) {
 			struct strbuf **split;
 			int result;
+			const char *input_merge_base = NULL;
 
 			split = strbuf_split(&buf, ' ');
-			if (!split[0] || !split[1] || split[2])
+			if (!split[0] || !split[1])
 				die(_("malformed input line: '%s'."), buf.buf);
 			strbuf_rtrim(split[0]);
-			result = real_merge(&o, merge_base, split[0]->buf, split[1]->buf, prefix);
+			strbuf_rtrim(split[1]);
+
+			/* parse the merge-base */
+			if (!strcmp(split[1]->buf, "--")) {
+				input_merge_base = split[0]->buf;
+			}
+
+			if (input_merge_base && split[2] && split[3] && !split[4]) {
+				strbuf_rtrim(split[2]);
+				strbuf_rtrim(split[3]);
+				result = real_merge(&o, input_merge_base, split[2]->buf, split[3]->buf, prefix);
+			} else if (!input_merge_base && !split[2]) {
+				result = real_merge(&o, NULL, split[0]->buf, split[1]->buf, prefix);
+			} else {
+				die(_("malformed input line: '%s'."), buf.buf);
+			}
+
 			if (result < 0)
 				die(_("merging cannot continue; got unclean result of %d"), result);
 			strbuf_list_free(split);