[PATCH 4/4] unpack-trees: support super-prefix option

[Stefan Beller <sbeller@google.com>]

Add support for the super-prefix option for commands that unpack trees.
For testing purposes enable it in read-tree, which has no other path
related output.

Signed-off-by: Stefan Beller <sbeller@google.com>
---
 git.c                       |  2 +-
 t/t1001-read-tree-m-2way.sh |  9 +++++++++
 unpack-trees.c              | 39 ++++++++++++++++++++++++++++++++++++---
 3 files changed, 46 insertions(+), 4 deletions(-)

diff --git a/git.c b/git.c
index dce529fcbf..acbabd1298 100644
--- a/git.c
+++ b/git.c
@@ -471,7 +471,7 @@ static struct cmd_struct commands[] = {
 	{ "prune-packed", cmd_prune_packed, RUN_SETUP },
 	{ "pull", cmd_pull, RUN_SETUP | NEED_WORK_TREE },
 	{ "push", cmd_push, RUN_SETUP },
-	{ "read-tree", cmd_read_tree, RUN_SETUP },
+	{ "read-tree", cmd_read_tree, RUN_SETUP | SUPPORT_SUPER_PREFIX},
 	{ "receive-pack", cmd_receive_pack },
 	{ "reflog", cmd_reflog, RUN_SETUP },
 	{ "remote", cmd_remote, RUN_SETUP },
diff --git a/t/t1001-read-tree-m-2way.sh b/t/t1001-read-tree-m-2way.sh
index 7b70089705..014ba39420 100755
--- a/t/t1001-read-tree-m-2way.sh
+++ b/t/t1001-read-tree-m-2way.sh
@@ -363,6 +363,15 @@ test_expect_success 'a/b (untracked) vs a, plus c/d case test.' '
 	test -f a/b
 '
 
+cat <<-EOF >expect &&
+	error: Updating 'fictional/a' would lose untracked files in it
+EOF
+
+test_expect_success 'read-tree supports the super-prefix' '
+	test_must_fail git --super-prefix fictional/ read-tree -u -m "$treeH" "$treeM" 2>actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'a/b vs a, plus c/d case setup.' '
 	rm -f .git/index &&
 	rm -fr a &&
diff --git a/unpack-trees.c b/unpack-trees.c
index 7a6df99d10..bc56195e27 100644
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -52,6 +52,37 @@ static const char *unpack_plumbing_errors[NB_UNPACK_TREES_ERROR_TYPES] = {
 	  ? ((o)->msgs[(type)])      \
 	  : (unpack_plumbing_errors[(type)]) )
 
+static const char *super_prefixed(const char *path)
+{
+	/*
+	 * This is used for the error messages above.
+	 * We need to have exactly two buffer spaces.
+	 */
+	static struct strbuf buf[2] = {STRBUF_INIT, STRBUF_INIT};
+	static int super_prefix_len = -1;
+	static unsigned idx = 0;
+
+	if (!get_super_prefix())
+		return path;
+
+	if (super_prefix_len < 0) {
+		int i;
+
+		for (i = 0; i < ARRAY_SIZE(buf); i++)
+			strbuf_addstr(&buf[i], get_super_prefix());
+
+		super_prefix_len = strlen(get_super_prefix());
+	}
+
+	if (++idx >= ARRAY_SIZE(buf))
+		idx = 0;
+
+	strbuf_setlen(&buf[idx], super_prefix_len);
+	strbuf_addstr(&buf[idx], path);
+
+	return buf[idx].buf;
+}
+
 void setup_unpack_trees_porcelain(struct unpack_trees_options *opts,
 				  const char *cmd)
 {
@@ -172,7 +203,7 @@ static int add_rejected_path(struct unpack_trees_options *o,
 			     const char *path)
 {
 	if (!o->show_all_errors)
-		return error(ERRORMSG(o, e), path);
+		return error(ERRORMSG(o, e), super_prefixed(path));
 
 	/*
 	 * Otherwise, insert in a list for future display by
@@ -196,7 +227,7 @@ static void display_error_msgs(struct unpack_trees_options *o)
 			something_displayed = 1;
 			for (i = 0; i < rejects->nr; i++)
 				strbuf_addf(&path, "\t%s\n", rejects->items[i].string);
-			error(ERRORMSG(o, e), path.buf);
+			error(ERRORMSG(o, e), super_prefixed(path.buf));
 			strbuf_release(&path);
 		}
 		string_list_clear(rejects, 0);
@@ -1918,7 +1949,9 @@ int bind_merge(const struct cache_entry * const *src,
 			     o->merge_size);
 	if (a && old)
 		return o->gently ? -1 :
-			error(ERRORMSG(o, ERROR_BIND_OVERLAP), a->name, old->name);
+			error(ERRORMSG(o, ERROR_BIND_OVERLAP),
+			      super_prefixed(a->name),
+			      super_prefixed(old->name));
 	if (!a)
 		return keep_entry(old, o);
 	else
-- 
2.11.0.rc2.30.g7c4be45.dirty