[PATCH v12 01/15] test: add test cases for relative_path

@@ -12,6 +12,11 @@ norm_path() {
 	"test \"\$(test-path-utils normalize_path_copy '$1')\" = '$2'"
 }
 
+relative_path() {
+	test_expect_success $4 "relative path: $1 $2 => $3" \
+	"test \"\$(test-path-utils relative_path '$1' '$2')\" = '$3'"
+}
+
 # On Windows, we are using MSYS's bash, which mangles the paths.
 # Absolute paths are anchored at the MSYS installation directory,
 # which means that the path / accounts for this many characters:

@@ -183,4 +188,25 @@ test_expect_success SYMLINKS 'real path works on symlinks' '
 	test "$sym" = "$(test-path-utils real_path "$dir2/syml")"
 '
 
+relative_path /a/b/c/	/a/b/		c/
+relative_path /a/b/c/	/a/b		c/
+relative_path /a//b//c/	//a/b//		c/
+relative_path /a/b	/a/b		.
+relative_path /a/b/	/a/b		.
+relative_path /a	/a/b		/a
+relative_path /		/a/b/		/
+relative_path /a/c	/a/b/		/a/c
+relative_path /a/c	/a/b		/a/c
+relative_path /a/b	"<empty>"	/a/b
+relative_path /a/b 	"<null>"	/a/b
+relative_path "<empty>"	/a/b		"(empty)"
+relative_path "<empty>"	"<empty>"	"(empty)"
+relative_path "<empty>"	"<null>"	"(empty)"
+relative_path "<null>"	"<empty>"	"(null)"
+relative_path "<null>"	"<null>"	"(null)"
+
+test_expect_failure 'relative path: <null> /a/b => segfault' '
+	test-path-utils relative_path "<null>" "/a/b"
+'
+
 test_done

@@ -1,6 +1,19 @@
 #include "cache.h"
 #include "string-list.h"
 
+#define PARSE_ARGV_STRING(var, input) do { \
+	if (!strcmp(input, "<null>")) { \
+		var = NULL; \
+	} else if (!strcmp(input, "<empty>")) { \
+		var = ""; \
+	} else if (*input == '<' || *input == '(') { \
+		fprintf(stderr, "Bad value: %s\n", input); \
+		return 1; \
+	} else { \
+		var = input; \
+	} \
+} while (0)
+
 /*
  * A "string_list_each_func_t" function that normalizes an entry from
  * GIT_CEILING_DIRECTORIES.  If the path is unusable for some reason,

@@ -103,6 +116,18 @@ int main(int argc, char **argv)
 		return 0;
 	}
 
+	if (argc == 4 && !strcmp(argv[1], "relative_path")) {
+		const char *abs, *base, *rel;
+		PARSE_ARGV_STRING(abs, argv[2]);
+		PARSE_ARGV_STRING(base, argv[3]);
+		rel = relative_path(abs, base);
+		if (!rel)
+			puts("(null)");
+		else
+			puts(strlen(rel) > 0 ? rel : "(empty)");
+		return 0;
+	}
+
 	fprintf(stderr, "%s: unknown function name: %s\n", argv[0],
 		argv[1] ? argv[1] : "(there was none)");
 	return 1;