read_index_from: remove bogus errno assignments

These assignments comes from the very first commit e83c516 (Initial
revision of "git", the information manager from hell - 2005-04-07).
Back then we did not die() when errors happened so correct errno was
required.

Since 5d1a5c0 ([PATCH] Better error reporting for "git status" -
2005-10-01), read_index_from() learned to die rather than just return
-1 and these assignments became irrelevant. Remove them.

While at it, move die_errno() next to xmmap() call because it's the
mmap's error code that we care about. Otherwise if close(fd); fails,
it could overwrite mmap's errno.

Signed-off-by: Nguyễn Thái Ngọc Duy <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pclouds

read-cache.c

@@ -1274,11 +1274,9 @@ int read_index_from(struct index_state *istate, const char *path)
 	void *mmap;
 	size_t mmap_size;
 
-	errno = EBUSY;
 	if (istate->initialized)
 		return istate->cache_nr;
 
-	errno = ENOENT;
 	istate->timestamp.sec = 0;
 	istate->timestamp.nsec = 0;
 	fd = open(path, O_RDONLY);
@@ -1291,15 +1289,14 @@ int read_index_from(struct index_state *istate, const char *path)
 	if (fstat(fd, &st))
 		die_errno("cannot stat the open index");
 
-	errno = EINVAL;
 	mmap_size = xsize_t(st.st_size);
 	if (mmap_size < sizeof(struct cache_header) + 20)
 		die("index file smaller than expected");
 
 	mmap = xmmap(NULL, mmap_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
-	close(fd);
 	if (mmap == MAP_FAILED)
 		die_errno("unable to map index file");
+	close(fd);
 
 	hdr = mmap;
 	if (verify_hdr(hdr, mmap_size) < 0)
@@ -1358,7 +1355,6 @@ int read_index_from(struct index_state *istate, const char *path)
 
 unmap:
 	munmap(mmap, mmap_size);
-	errno = EINVAL;
 	die("index file corrupt");
 }