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

builtin/merge.c

@@ -839,9 +839,7 @@ static int suggest_conflicts(void)
 	struct strbuf msgbuf = STRBUF_INIT;
 
 	filename = git_path_merge_msg();
-	fp = fopen(filename, "a");
-	if (!fp)
-		die_errno(_("Could not open '%s' for writing"), filename);
+	fp = xfopen(filename, "a");
 
 	append_conflicts_hint(&msgbuf);
 	fputs(msgbuf.buf, fp);