[PATCH v6 1/7] setup: add gentle version of is_git_directory

["Erik Elfström" <erik.elfstrom@gmail.com>]

This is a prerequisite for implementing a gentle version of
read_gitfile.

Signed-off-by: Erik Elfström <erik.elfstrom@gmail.com>
---
 cache.h |  4 ++++
 setup.c | 44 +++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/cache.h b/cache.h
index b34447f..dd67695 100644
--- a/cache.h
+++ b/cache.h
@@ -431,7 +431,11 @@ extern int is_inside_git_dir(void);
 extern char *git_work_tree_cfg;
 extern int is_inside_work_tree(void);
 extern const char *get_git_dir(void);
+
+#define IS_GIT_DIRECTORY_ERR_PATH_TOO_LONG 1
+extern int is_git_directory_gently(const char *path, int *return_err, struct strbuf *err_msg);
 extern int is_git_directory(const char *path);
+
 extern char *get_object_directory(void);
 extern char *get_index_file(void);
 extern char *get_graft_file(void);
diff --git a/setup.c b/setup.c
index 979b13f..62ee88c 100644
--- a/setup.c
+++ b/setup.c
@@ -224,6 +224,18 @@ void verify_non_filename(const char *prefix, const char *arg)
 	    "'git <command> [<revision>...] -- [<file>...]'", arg);
 }
 
+__attribute((format (printf,4,5)))
+static void set_error(int *return_err, struct strbuf *err_msg, int err,
+		      const char *msg, ...)
+{
+	va_list params;
+	va_start(params, msg);
+	if (err_msg)
+		strbuf_vaddf(err_msg, msg, params);
+	va_end(params);
+	if (return_err)
+		*return_err = err;
+}
 
 /*
  * Test if it looks like we're at a git directory.
@@ -235,14 +247,28 @@ void verify_non_filename(const char *prefix, const char *arg)
  *  - either a HEAD symlink or a HEAD file that is formatted as
  *    a proper "ref:", or a regular file HEAD that has a properly
  *    formatted sha1 object name.
+ *
+ * In the event of an error, return_err will be set to an error code
+ * and err_msg will be set to an error message describing the error
+ * and 0 will be returned. If no error reporting is required, pass
+ * NULL for return_err and/or err_msg.
  */
-int is_git_directory(const char *suspect)
+int is_git_directory_gently(const char *suspect, int *return_err,
+			    struct strbuf *err_msg)
 {
 	char path[PATH_MAX];
 	size_t len = strlen(suspect);
 
-	if (PATH_MAX <= len + strlen("/objects"))
-		die("Too long path: %.*s", 60, suspect);
+	if (return_err)
+		*return_err = 0;
+
+	if (PATH_MAX <= len + strlen("/objects")) {
+		set_error(return_err, err_msg,
+			  IS_GIT_DIRECTORY_ERR_PATH_TOO_LONG,
+			  "Too long path: %.*s", 60, suspect);
+		return 0;
+	}
+
 	strcpy(path, suspect);
 	if (getenv(DB_ENVIRONMENT)) {
 		if (access(getenv(DB_ENVIRONMENT), X_OK))
@@ -265,6 +291,18 @@ int is_git_directory(const char *suspect)
 	return 1;
 }
 
+int is_git_directory(const char *suspect)
+{
+	int err;
+	int ret;
+	struct strbuf err_msg = STRBUF_INIT;
+	ret = is_git_directory_gently(suspect, &err, &err_msg);
+	if (err)
+		die("%s", err_msg.buf);
+	/* No need to free err_msg, will only be touched in case of error */
+	return ret;
+}
+
 int is_inside_git_dir(void)
 {
 	if (inside_git_dir < 0)
-- 
2.4.0.60.gf7143f7