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

wrapper.c

@@ -418,6 +418,32 @@ FILE *fopen_for_writing(const char *path)
 	return ret;
 }
 
+static void warn_on_inaccessible(const char *path)
+{
+	warning_errno(_("unable to access '%s'"), path);
+}
+
+int warn_on_fopen_errors(const char *path)
+{
+	if (errno != ENOENT && errno != ENOTDIR) {
+		warn_on_inaccessible(path);
+		return -1;
+	}
+
+	return 0;
+}
+
+FILE *fopen_or_warn(const char *path, const char *mode)
+{
+	FILE *fp = fopen(path, mode);
+
+	if (fp)
+		return fp;
+
+	warn_on_fopen_errors(path);
+	return NULL;
+}
+
 int xmkstemp(char *template)
 {
 	int fd;
@@ -576,11 +602,6 @@ int remove_or_warn(unsigned int mode, const char *file)
 	return S_ISGITLINK(mode) ? rmdir_or_warn(file) : unlink_or_warn(file);
 }
 
-void warn_on_inaccessible(const char *path)
-{
-	warning_errno(_("unable to access '%s'"), path);
-}
-
 static int access_error_is_ok(int err, unsigned flag)
 {
 	return (is_missing_file_error(err) ||