1 files changed, 32 insertions, 0 deletions
diff --git a/setup.c b/setup.c
index 5ea5502e48..2c51a9a4c7 100644
--- a/setup.c
+++ b/setup.c
@@ -264,6 +264,38 @@ const char **get_pathspec(const char *prefix, const char **pathspec)
 	return pathspec;
 }
 
+const char *pathspec_prefix(const char *prefix, const char **pathspec)
+{
+	const char **p, *n, *prev;
+	unsigned long max;
+
+	if (!pathspec)
+		return prefix ? xmemdupz(prefix, strlen(prefix)) : NULL;
+
+	prev = NULL;
+	max = PATH_MAX;
+	for (p = pathspec; (n = *p) != NULL; p++) {
+		int i, len = 0;
+		for (i = 0; i < max; i++) {
+			char c = n[i];
+			if (prev && prev[i] != c)
+				break;
+			if (!c || c == '*' || c == '?')
+				break;
+			if (c == '/')
+				len = i+1;
+		}
+		prev = n;
+		if (len < max) {
+			max = len;
+			if (!max)
+				break;
+		}
+	}
+
+	return max ? xmemdupz(prev, max) : NULL;
+}
+
 /*
  * Test if it looks like we're at a git directory.
  * We want to see: