[GSoC] cache.h: change READ_GITFILE_ERR constants group to enum

[sheikh hamza <sheikhhamza012@gmail.com>]

this patch is my microproject for the GSoC i converted
the group of constants in cache.h on line 573 to an enum
named read_gitfile_err to follow newer coding convension
i intend to contribute as much to git as i can and this is
my initial contribution i hope to get guidance for future
contribution. i would be working on the GSoC proposal any
help would be appreciated, Thank you

Signed-off-by: Muhammad Hamza <sheikhhamza012@gmail.com>
---
 cache.h | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/cache.h b/cache.h
index 37c899b..6aae035 100644
--- a/cache.h
+++ b/cache.h
@@ -570,14 +570,17 @@ static inline enum object_type object_type(unsigned int mode)
  */
 int is_nonbare_repository_dir(struct strbuf *path);
 
-#define READ_GITFILE_ERR_STAT_FAILED 1
-#define READ_GITFILE_ERR_NOT_A_FILE 2
-#define READ_GITFILE_ERR_OPEN_FAILED 3
-#define READ_GITFILE_ERR_READ_FAILED 4
-#define READ_GITFILE_ERR_INVALID_FORMAT 5
-#define READ_GITFILE_ERR_NO_PATH 6
-#define READ_GITFILE_ERR_NOT_A_REPO 7
-#define READ_GITFILE_ERR_TOO_LARGE 8
+enum read_gitfile_err {
+	READ_GITFILE_ERR_STAT_FAILED = 1,
+	READ_GITFILE_ERR_NOT_A_FILE = 2,
+	READ_GITFILE_ERR_OPEN_FAILED = 3,
+	READ_GITFILE_ERR_READ_FAILED = 4,
+	READ_GITFILE_ERR_INVALID_FORMAT = 5,
+	READ_GITFILE_ERR_NO_PATH = 6,
+	READ_GITFILE_ERR_NOT_A_REPO = 7,
+	READ_GITFILE_ERR_TOO_LARGE = 8,
+};
+
 void read_gitfile_error_die(int error_code, const char *path, const char *dir);
 const char *read_gitfile_gently(const char *path, int *return_error_code);
 #define read_gitfile(path) read_gitfile_gently((path), NULL)
-- 
1.9.1