Skip read-only check when output file specified

Only check if input files are read-only when overwriting them; skip
that check when the output goes to a different file.

* src/patch.c (main): Set read_only_behavior to RO_IGNORE when an output
file has been specified.
* tests/read-only-files: Add test case.

NEWS

@@ -1,3 +1,5 @@
+Unreleased changes:
+
 Changes in version 2.8:
 
 * The --follow-symlinks option now applies to output files as well as input.

cfg.mk

@@ -18,6 +18,8 @@ config_h_header = <(common|config)\.h>
 
 ifeq ($(RELEASE_TYPE),alpha)
   news-check-regexp = "Unreleased changes"
+else
+  news-check-regexp = '^Changes in version $(VERSION_REGEXP):'
 endif
 
 release-prep-hook =

src/patch.c

@@ -204,7 +204,10 @@ main (int argc, char **argv)
 
     init_output (&outstate);
     if (outfile)
-      outstate.ofp = open_outfile (outfile);
+      {
+        outstate.ofp = open_outfile (outfile);
+        read_only_behavior = RO_IGNORE;
+      }
 
     /* Make sure we clean up in case of disaster.  */
     init_signals ();
@@ -323,7 +326,8 @@ main (int argc, char **argv)
 	    }
 	}
 
-      if (read_only_behavior != RO_IGNORE
+      if (! skip_rest_of_patch
+	  && read_only_behavior != RO_IGNORE
 	  && ! inerrno && ! S_ISLNK (instat.st_mode)
 	  && safe_access (inname, W_OK) != 0)
 	{
@@ -616,7 +620,7 @@ main (int argc, char **argv)
 		      struct stat outstat;
 
 		      if (stat_file (outname, &outstat) != 0)
-			say ("Cannot stat file %s, skipping backup\n", outname);
+			say ("Cannot stat file %s, skipping backup\n", quotearg (outname));
 		      else
 			output_file (&(struct outfile) { .name = outname },
 				     &outstat, nullptr, nullptr,

src/safe.c

@@ -571,6 +571,8 @@ safe_xstat (char *pathname, struct stat *buf, int flags)
   int dirfd = traverse_path (&pathname, false);
   if (dirfd == DIRFD_INVALID)
     return -1;
+  if (! strcmp (pathname, ""))
+    return EINVAL;
   return fstatat (dirfd, pathname, buf, flags);
 }
 

tests/bad-filenames

@@ -200,3 +200,11 @@ No file to patch.  Skipping patch.
 1 out of 1 hunk ignored
 status: 1
 EOF
+
+# Empty filenames are not allowed:
+
+check 'emit_patch f | patch -r- "" || echo status: $?' <<EOF
+File '' is not a regular file -- refusing to patch
+1 out of 1 hunk ignored
+status: 1
+EOF

tests/read-only-files

@@ -67,3 +67,8 @@ check 'patch -f -p0 --read-only=ignore < f.diff || echo "Status: $?"' <<EOF
 patching file f
 patching file f
 EOF
+
+check 'patch -o - f /dev/null || echo "Status: $?"' <<EOF
+patching file - (read from f)
+three
+EOF