Fix git-fetch while on detached HEAD not to give needlessly alarming errors

When we are on a detached HEAD, there is no current branch.
There is no reason to leak the error messages to the end user
since this is a situation we expect to see.

This adds -q option to git-symbolic-ref to exit without issuing
an error message if the given name is not a symbolic ref.

By the way, with or without this patch, there currently is no
good way to tell failure modes between "git symbolic-ref HAED"
and "git symbolic-ref HEAD".  Both says "is not a symbolic ref".

We may want to do something about it.

Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/git-symbolic-ref.txt

@@ -7,7 +7,7 @@ git-symbolic-ref - read and modify symbolic refs
 
 SYNOPSIS
 --------
-'git-symbolic-ref' <name> [<ref>]
+'git-symbolic-ref' [-q] <name> [<ref>]
 
 DESCRIPTION
 -----------
@@ -23,6 +23,14 @@ A symbolic ref is a regular file that stores a string that
 begins with `ref: refs/`.  For example, your `.git/HEAD` is
 a regular file whose contents is `ref: refs/heads/master`.
 
+OPTIONS
+-------
+
+-q::
+	Do not issue an error message if the <name> is not a
+	symbolic ref but a detached HEAD; instead exit with
+	non-zero status silently.
+
 NOTES
 -----
 In the past, `.git/HEAD` was a symbolic link pointing at

builtin-symbolic-ref.c

@@ -3,9 +3,9 @@
 #include "refs.h"
 
 static const char git_symbolic_ref_usage[] =
-"git-symbolic-ref name [ref]";
+"git-symbolic-ref [-q] name [ref]";
 
-static void check_symref(const char *HEAD)
+static void check_symref(const char *HEAD, int quiet)
 {
 	unsigned char sha1[20];
 	int flag;
@@ -13,17 +13,41 @@ static void check_symref(const char *HEAD)
 
 	if (!refs_heads_master)
 		die("No such ref: %s", HEAD);
-	else if (!(flag & REF_ISSYMREF))
+	else if (!(flag & REF_ISSYMREF)) {
-		die("ref %s is not a symbolic ref", HEAD);
+		if (!quiet)
+			die("ref %s is not a symbolic ref", HEAD);
+		else
+			exit(1);
+	}
 	puts(refs_heads_master);
 }
 
 int cmd_symbolic_ref(int argc, const char **argv, const char *prefix)
 {
+	int quiet = 0;
+
 	git_config(git_default_config);
+
+	while (1 < argc) {
+		const char *arg = argv[1];
+		if (arg[0] != '-')
+			break;
+		else if (!strcmp("-q", arg))
+			quiet = 1;
+		else if (!strcmp("--", arg)) {
+			argc--;
+			argv++;
+			break;
+		}
+		else
+			die("unknown option %s", arg);
+		argc--;
+		argv++;
+	}
+
 	switch (argc) {
 	case 2:
-		check_symref(argv[1]);
+		check_symref(argv[1], quiet);
 		break;
 	case 3:
 		create_symref(argv[1], argv[2]);

git-parse-remote.sh

@@ -49,7 +49,7 @@ get_remote_url () {
 }
 
 get_default_remote () {
-	curr_branch=$(git-symbolic-ref HEAD | sed -e 's|^refs/heads/||')
+	curr_branch=$(git-symbolic-ref -q HEAD | sed -e 's|^refs/heads/||')
 	origin=$(git-repo-config --get "branch.$curr_branch.remote")
 	echo ${origin:-origin}
 }
@@ -137,7 +137,7 @@ canon_refs_list_for_fetch () {
 		shift
 		if test "$remote" = "$(get_default_remote)"
 		then
-			curr_branch=$(git-symbolic-ref HEAD | \
+			curr_branch=$(git-symbolic-ref -q HEAD | \
 			    sed -e 's|^refs/heads/||')
 			merge_branches=$(git-repo-config \
 			    --get-all "branch.${curr_branch}.merge")