Merge branch 'jn/show-normalized-refs'

* jn/show-normalized-refs:
  check-ref-format: simplify --print implementation
  git check-ref-format --print
  Add tests for git check-ref-format

Conflicts:
	Documentation/git-check-ref-format.txt

3 files changed, 111 insertions, 6 deletions

diff --git a/Documentation/git-check-ref-format.txt b/Documentation/git-check-ref-format.txt
index e9b3b40af4..0aeef24780 100644
--- a/Documentation/git-check-ref-format.txt
+++ b/Documentation/git-check-ref-format.txt
@@ -9,6 +9,7 @@ SYNOPSIS
 --------
 [verse]
 'git check-ref-format' <refname>
+'git check-ref-format' --print <refname>
 'git check-ref-format' --branch <branchname-shorthand>
 
 DESCRIPTION
@@ -63,19 +64,31 @@ reference name expressions (see linkgit:git-rev-parse[1]):
 
 . at-open-brace `@{` is used as a notation to access a reflog entry.
 
+With the `--print` option, if 'refname' is acceptable, it prints the
+canonicalized name of a hypothetical reference with that name.  That is,
+it prints 'refname' with any extra `/` characters removed.
+
 With the `--branch` option, it expands the ``previous branch syntax''
 `@{-n}`.  For example, `@{-1}` is a way to refer the last branch you
 were on.  This option should be used by porcelains to accept this
 syntax anywhere a branch name is expected, so they can act as if you
 typed the branch name.
 
-EXAMPLE
--------
-
-git check-ref-format --branch @{-1}::
-
-Print the name of the previous branch.
+EXAMPLES
+--------
 
+* Print the name of the previous branch:
++
+------------
+$ git check-ref-format --branch @{-1}
+------------
+
+* Determine the reference name to use for a new branch:
++
+------------
+$ ref=$(git check-ref-format --print "refs/heads/$newbranch") ||
+die "we do not like '$newbranch' as a branch name."
+------------
 
 GIT
 ---
diff --git a/builtin-check-ref-format.c b/builtin-check-ref-format.c
index f9381e07ea..e3e7bdf52f 100644
--- a/builtin-check-ref-format.c
+++ b/builtin-check-ref-format.c
@@ -7,6 +7,28 @@
 #include "builtin.h"
 #include "strbuf.h"
 
+/*
+ * Replace each run of adjacent slashes in src with a single slash,
+ * and write the result to dst.
+ *
+ * This function is similar to normalize_path_copy(), but stripped down
+ * to meet check_ref_format's simpler needs.
+ */
+static void collapse_slashes(char *dst, const char *src)
+{
+	char ch;
+	char prev = '\0';
+
+	while ((ch = *src++) != '\0') {
+		if (prev == '/' && ch == prev)
+			continue;
+
+		*dst++ = ch;
+		prev = ch;
+	}
+	*dst = '\0';
+}
+
 int cmd_check_ref_format(int argc, const char **argv, const char *prefix)
 {
 	if (argc == 3 && !strcmp(argv[1], "--branch")) {
@@ -17,6 +39,15 @@ int cmd_check_ref_format(int argc, const char **argv, const char *prefix)
 		printf("%s\n", sb.buf + 11);
 		exit(0);
 	}
+	if (argc == 3 && !strcmp(argv[1], "--print")) {
+		char *refname = xmalloc(strlen(argv[2]) + 1);
+
+		if (check_ref_format(argv[2]))
+			exit(1);
+		collapse_slashes(refname, argv[2]);
+		printf("%s\n", refname);
+		exit(0);
+	}
 	if (argc != 2)
 		usage("git check-ref-format refname");
 	return !!check_ref_format(argv[1]);
diff --git a/t/t1402-check-ref-format.sh b/t/t1402-check-ref-format.sh
new file mode 100644
index 0000000000..eb45afb018
--- /dev/null
+++ b/t/t1402-check-ref-format.sh
@@ -0,0 +1,61 @@
+#!/bin/sh
+
+test_description='Test git check-ref-format'
+
+. ./test-lib.sh
+
+valid_ref() {
+	test_expect_success "ref name '$1' is valid" \
+		"git check-ref-format '$1'"
+}
+invalid_ref() {
+	test_expect_success "ref name '$1' is not valid" \
+		"test_must_fail git check-ref-format '$1'"
+}
+
+valid_ref 'heads/foo'
+invalid_ref 'foo'
+valid_ref 'foo/bar/baz'
+valid_ref 'refs///heads/foo'
+invalid_ref 'heads/foo/'
+invalid_ref './foo'
+invalid_ref '.refs/foo'
+invalid_ref 'heads/foo..bar'
+invalid_ref 'heads/foo?bar'
+valid_ref 'foo./bar'
+invalid_ref 'heads/foo.lock'
+valid_ref 'heads/foo@bar'
+invalid_ref 'heads/v@{ation'
+invalid_ref 'heads/foo\bar'
+
+test_expect_success "check-ref-format --branch @{-1}" '
+	T=$(git write-tree) &&
+	sha1=$(echo A | git commit-tree $T) &&
+	git update-ref refs/heads/master $sha1 &&
+	git update-ref refs/remotes/origin/master $sha1
+	git checkout master &&
+	git checkout origin/master &&
+	git checkout master &&
+	refname=$(git check-ref-format --branch @{-1}) &&
+	test "$refname" = "$sha1" &&
+	refname2=$(git check-ref-format --branch @{-2}) &&
+	test "$refname2" = master'
+
+valid_ref_normalized() {
+	test_expect_success "ref name '$1' simplifies to '$2'" "
+		refname=\$(git check-ref-format --print '$1') &&
+		test \"\$refname\" = '$2'"
+}
+invalid_ref_normalized() {
+	test_expect_success "check-ref-format --print rejects '$1'" "
+		test_must_fail git check-ref-format --print '$1'"
+}
+
+valid_ref_normalized 'heads/foo' 'heads/foo'
+valid_ref_normalized 'refs///heads/foo' 'refs/heads/foo'
+invalid_ref_normalized 'foo'
+invalid_ref_normalized 'heads/foo/../bar'
+invalid_ref_normalized 'heads/./foo'
+invalid_ref_normalized 'heads\foo'
+
+test_done