rename pathspec_prefix() to common_prefix() and move to dir.[ch]

Also make common_prefix_len() static as this refactoring makes dir.c
itself the only caller of this helper function.
Signed-off-by: NClemens Buchacher <drizzd@aon.at>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin/commit.c

@@ -257,7 +257,7 @@ static int list_paths(struct string_list *list, const char *with_tree,
 	m = xcalloc(1, i);
 
 	if (with_tree) {
-		char *max_prefix = pathspec_prefix(pattern);
+		char *max_prefix = common_prefix(pattern);
 		overlay_tree_on_cache(with_tree, max_prefix ? max_prefix : prefix);
 		free(max_prefix);
 	}

builtin/ls-files.c

@@ -541,7 +541,7 @@ int cmd_ls_files(int argc, const char **argv, const char *cmd_prefix)
 		strip_trailing_slash_from_submodules();
 
 	/* Find common prefix for all pathspec's */
-	max_prefix = pathspec_prefix(pathspec);
+	max_prefix = common_prefix(pathspec);
 	max_prefix_len = max_prefix ? strlen(max_prefix) : 0;
 
 	/* Treat unmatching pathspec elements as errors */

cache.h

@@ -426,7 +426,6 @@ extern void set_git_work_tree(const char *tree);
 #define ALTERNATE_DB_ENVIRONMENT "GIT_ALTERNATE_OBJECT_DIRECTORIES"
 
 extern const char **get_pathspec(const char *prefix, const char **pathspec);
-extern char *pathspec_prefix(const char **pathspec);
 extern void setup_work_tree(void);
 extern const char *setup_git_directory_gently(int *);
 extern const char *setup_git_directory(void);

dir.c

@@ -34,7 +34,7 @@ int fnmatch_icase(const char *pattern, const char *string, int flags)
 	return fnmatch(pattern, string, flags | (ignore_case ? FNM_CASEFOLD : 0));
 }
 
-size_t common_prefix_len(const char **pathspec)
+static size_t common_prefix_len(const char **pathspec)
 {
 	const char *n, *first;
 	size_t max = 0;
@@ -61,6 +61,17 @@ size_t common_prefix_len(const char **pathspec)
 	return max;
 }
 
+/*
+ * Returns a copy of the longest leading path common among all
+ * pathspecs.
+ */
+char *common_prefix(const char **pathspec)
+{
+	unsigned long len = common_prefix_len(pathspec);
+
+	return len ? xmemdupz(*pathspec, len) : NULL;
+}
+
 int fill_directory(struct dir_struct *dir, const char **pathspec)
 {
 	const char *path;

dir.h

@@ -64,7 +64,7 @@ struct dir_struct {
 #define MATCHED_RECURSIVELY 1
 #define MATCHED_FNMATCH 2
 #define MATCHED_EXACTLY 3
-extern size_t common_prefix_len(const char **pathspec);
+extern char *common_prefix(const char **pathspec);
 extern int match_pathspec(const char **pathspec, const char *name, int namelen, int prefix, char *seen);
 extern int match_pathspec_depth(const struct pathspec *pathspec,
 				const char *name, int namelen,

setup.c

@@ -264,13 +264,6 @@ const char **get_pathspec(const char *prefix, const char **pathspec)
 	return pathspec;
 }
 
-char *pathspec_prefix(const char **pathspec)
-{
-	size_t len = common_prefix_len(pathspec);
-
-	return len ? xmemdupz(*pathspec, len) : NULL;
-}
-
 /*
  * Test if it looks like we're at a git directory.
  * We want to see: