Simplify the way 'got patch' opens a tempfile when reading from stdin.
Also add basic test coverage for reading patches from stdin, while here.

Noticed while looking for calls to unlink() which lack any error checking.
 
diff d2533287ff253bfb6fe08ddc0005ac3349fdf38c 557647147e5a1df9302c01776f6ee9a99815e3b5
commit - d2533287ff253bfb6fe08ddc0005ac3349fdf38c
commit + 557647147e5a1df9302c01776f6ee9a99815e3b5
blob - ef5a8b59c5e55dfdeec6f464375604437cc707d8
blob + 913aa0d9c49c4d45eb2e7eaef91e7df770fd734a
--- got/got.c
+++ got/got.c
@@ -7862,15 +7862,12 @@ patch_from_stdin(int *patchfd)
 {
 	const struct got_error *err = NULL;
 	ssize_t r;
-	char *path, buf[BUFSIZ];
+	char buf[BUFSIZ];
 	sig_t sighup, sigint, sigquit;
 
-	err = got_opentemp_named_fd(&path, patchfd,
-	    GOT_TMPDIR_STR "/got-patch");
-	if (err)
-		return err;
-	unlink(path);
-	free(path);
+	*patchfd = got_opentempfd();
+	if (*patchfd == -1)
+		return got_error_from_errno("got_opentemp_fd");
 
 	sighup = signal(SIGHUP, SIG_DFL);
 	sigint = signal(SIGINT, SIG_DFL);
blob - 1bcdb584a653439ff381dc63d0dc88145ee8fa36
blob + f8f949b792887413b26e30cab123e9e1c57ae123
--- regress/cmdline/patch.sh
+++ regress/cmdline/patch.sh
@@ -87,7 +87,7 @@ EOF
 +103
 EOF
 
-	(cd $testroot/wt && got patch patch) > $testroot/stdout
+	(cd $testroot/wt && got patch < patch) > $testroot/stdout
 	if [ $ret -ne 0 ]; then
 		test_done "$testroot" $ret
 		return 1