Merge branch 'nd/fopen-errors'

We often try to open a file for reading whose existence is
optional, and silently ignore errors from open/fopen; report such
errors if they are not due to missing files.

* nd/fopen-errors:
  mingw_fopen: report ENOENT for invalid file names
  mingw: verify that paths are not mistaken for remote nicknames
  log: fix memory leak in open_next_file()
  rerere.c: move error_errno() closer to the source system call
  print errno when reporting a system call error
  wrapper.c: make warn_on_inaccessible() static
  wrapper.c: add and use fopen_or_warn()
  wrapper.c: add and use warn_on_fopen_errors()
  config.mak.uname: set FREAD_READS_DIRECTORIES for Darwin, too
  config.mak.uname: set FREAD_READS_DIRECTORIES for Linux and FreeBSD
  clone: use xfopen() instead of fopen()
  use xfopen() in more places
  git_fopen: fix a sparse 'not declared' warning

commit.c

@@ -168,7 +168,7 @@ bad_graft_data:
 
 static int read_graft_file(const char *graft_file)
 {
-	FILE *fp = fopen(graft_file, "r");
+	FILE *fp = fopen_or_warn(graft_file, "r");
 	struct strbuf buf = STRBUF_INIT;
 	if (!fp)
 		return -1;