[PATCH 5/5] get_sha1: allow custom ref mapping with $ref@{~alias} syntax

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

Similar to $SHA1^{~alias}, the alias is defined as ref.alias. It is
supposed to return something that can resolve to a ref.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation/config.txt    |    9 +++++
 Documentation/revisions.txt |    5 +++
 alias.c                     |    5 +++
 cache.h                     |    1 +
 sha1_name.c                 |   70 +++++++++++++++++++++++++++++++++++++++++-
 t/t1512-rev-parse-at.sh     |   63 ++++++++++++++++++++++++++++++++++++++
 6 files changed, 151 insertions(+), 2 deletions(-)
 create mode 100755 t/t1512-rev-parse-at.sh

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 0c4fb66..a20b467 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -597,6 +597,15 @@ sha1.*::
 	alias command will be substituted with 'extra'. The command is
 	supposed to return an extended SHA-1 syntax.
 
+ref.*::
+	Ref translation aliases. These aliases are similar to alias.*
+	but each will correspond to a '@\{{tilde}alias\}' syntax (see
+	linkgit:gitrevisions[7]). '%ref%' in the alias command will be
+	substituted with the ref before the '@'. If
+	'@\{{tilde}alias:extra\}' syntax is used, '%arg%' in the alias
+	command will be substituted with 'extra'. The command is supposed
+	to return a ref.
+
 am.keepcr::
 	If true, git-am will call git-mailsplit for patches in mbox format
 	with parameter '--keep-cr'. In this case git-mailsplit will
diff --git a/Documentation/revisions.txt b/Documentation/revisions.txt
index 413f91c..86b0b63 100644
--- a/Documentation/revisions.txt
+++ b/Documentation/revisions.txt
@@ -80,6 +80,11 @@ the `$GIT_DIR/refs` directory or from the `$GIT_DIR/packed-refs` file.
   the branch the ref is set to build on top of.  Missing ref defaults
   to the current branch.
 
+* A ref followed by '@\{{tilde}alias\}' will invoke the corresponding
+  alias command, specified in config (see linkgit:git-config[1],
+  key 'ref.*'). The command is supposed to return a ref. The
+  result ref can contain '@\{..\}' syntax.
+
 * A suffix '{caret}' to a revision parameter (e.g. 'HEAD{caret}') means the first parent of
   that commit object.  '{caret}<n>' means the <n>th parent (i.e.
   'rev{caret}'
diff --git a/alias.c b/alias.c
index 29a9903..242401e 100644
--- a/alias.c
+++ b/alias.c
@@ -36,6 +36,11 @@ char *sha1_alias_lookup(const char *alias)
 	return generic_alias_lookup(alias, "sha1.");
 }
 
+char *ref_alias_lookup(const char *alias)
+{
+	return generic_alias_lookup(alias, "ref.");
+}
+
 #define SPLIT_CMDLINE_BAD_ENDING 1
 #define SPLIT_CMDLINE_UNCLOSED_QUOTE 2
 static const char *split_cmdline_errors[] = {
diff --git a/cache.h b/cache.h
index 56a1b18..1d4ce65 100644
--- a/cache.h
+++ b/cache.h
@@ -1121,6 +1121,7 @@ struct alias_param {
 
 char *alias_lookup(const char *alias);
 char *sha1_alias_lookup(const char *alias);
+char *ref_alias_lookup(const char *alias);
 int split_cmdline(char *cmdline, const char ***argv);
 /* Takes a negative value returned by split_cmdline */
 const char *split_cmdline_strerror(int cmdline_errno);
diff --git a/sha1_name.c b/sha1_name.c
index cdf14c7..2734f24 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -359,7 +359,8 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 	if (len && str[len-1] == '}') {
 		for (at = len-2; at >= 0; at--) {
 			if (str[at] == '@' && str[at+1] == '{') {
-				if (!upstream_mark(str + at, len - at)) {
+				if (!upstream_mark(str + at, len - at) &&
+				    str[at+2] != '~') {
 					reflog_len = (len-1) - (at+2);
 					len = at;
 				}
@@ -994,6 +995,69 @@ static int interpret_at_upstream(const char *at, struct strbuf *real_ref)
 	return len;
 }
 
+static int interpret_at_alias(const char *at, struct strbuf *real_ref)
+{
+	struct alias_param *params, *param;
+	struct strbuf alias = STRBUF_INIT;
+	struct strbuf cmd = STRBUF_INIT;
+	char *s;
+	int ret, len, arg_len = 0;
+
+	if (at[1] != '{' || at[2] != '~')
+		return -1;
+	len = strcspn(at + 3, ":}");
+	if (!len)
+		return error("$ref@{~alias} syntax with no alias");
+	if (at[3 + len] == ':') {
+		s = strchr(at + 3 + len + 1, '}');
+		if (!s)
+			return error("$ref@{~alias} does not end with }");
+		arg_len = s - at - (3 + len + 1);
+	}
+	strbuf_add(&alias, at + 3, len);
+	s = ref_alias_lookup(alias.buf);
+	if (!s) {
+		ret = error("unable to find ref alias '%s'", alias.buf);
+		goto done;
+	}
+
+	strbuf_attach(&cmd, s, strlen(s), strlen(s)+1);
+	extract_alias_params(cmd.buf, &params);
+	param = lookup_alias_param(params, "%ref%");
+	if (param && real_ref->len)
+		param->value = xstrdup(real_ref->buf);
+	else if (param) {
+		ret = error("%%ref%% not found in alias '%s'", cmd.buf);
+		goto done;
+	}
+	else if (real_ref->len) {
+		ret = error("%%ref%% is required but alias '%s' is not followed by a ref", cmd.buf);
+		goto done;
+	}
+	param = lookup_alias_param(params, "%arg%");
+	if (param && arg_len) {
+		param->value = xstrndup(at + len + 4, arg_len);
+		len += arg_len + 1;
+	}
+	else if (param) {
+		ret = error("Alias '%s' needs arguments", alias.buf);
+		goto done;
+	}
+	else if (arg_len) {
+		ret = error("Arguments are given but alias '%s' does not need them", alias.buf);
+		goto done;
+	}
+	expand_alias_params(&cmd, params);
+	free_alias_params(params);
+
+	trace_printf("trace: ref alias expansion: %s => %s\n", alias.buf, cmd.buf);
+	ret = get_alias_oneline(alias.buf, cmd.buf, real_ref) ? -1 : len + 4;
+done:
+	strbuf_release(&alias);
+	strbuf_release(&cmd);
+	return ret;
+}
+
 /*
  * This reads short-hand syntax that not only evaluates to a commit
  * object name, but also can act as if the end user spelled the name
@@ -1035,6 +1099,8 @@ int interpret_branch_name(const char *name, struct strbuf *buf)
 
 	if (len == -1)
 		len = interpret_at_upstream(cp, buf);
+	if (len == -1)
+		len = interpret_at_alias(cp, buf);
 	if (len == -1) {
 		strbuf_reset(buf);
 		return -1;
@@ -1044,7 +1110,7 @@ int interpret_branch_name(const char *name, struct strbuf *buf)
 		return len; /* syntax Ok, not enough switches */
 
 	used += len;
-	if (used == namelen)
+	if (used == namelen && !strstr(buf->buf, "@{"))
 		return used; /* consumed all */
 
 	/* we have extra data, which might need further processing */
diff --git a/t/t1512-rev-parse-at.sh b/t/t1512-rev-parse-at.sh
new file mode 100755
index 0000000..6594146
--- /dev/null
+++ b/t/t1512-rev-parse-at.sh
@@ -0,0 +1,63 @@
+#!/bin/sh
+
+test_description='tests for $ref@{something}'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	test_commit foo &&
+	git branch foo &&
+	test_commit bar &&
+	git branch bar &&
+	test_commit zoo-bar &&
+	git branch zoo/bar &&
+	test_commit zoo-zoo-bar &&
+	git branch zoo/zoo/bar
+'
+
+test_expect_success 'ref@{~}' '
+	test_must_fail git rev-parse HEAD@{~}
+'
+
+test_expect_success 'ref@{~non-existent}' '
+	test_must_fail git rev-parse HEAD@{~non-existent}
+'
+
+test_expect_success 'ref@{~simple}' '
+	git config ref.simple "symbolic-ref %ref%" &&
+	test_must_fail git rev-parse HEAD@{~simple:something} &&
+	git rev-parse HEAD@{~simple} >actual &&
+	git rev-parse HEAD >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success 'ref@{~external}' '
+	git config ref.external "!echo zoo/%ref%" &&
+	test_must_fail git rev-parse bar@{~external:something} &&
+	git rev-parse bar@{~external} >actual &&
+	git rev-parse zoo/bar >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success 'ref@{~witharg:args}' '
+	git config ref.witharg "!echo %ref%/%arg%" &&
+	test_must_fail git rev-parse zoo@{~witharg} &&
+	git rev-parse zoo@{~witharg:bar} >actual &&
+	git rev-parse zoo/bar >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success 'ref@{~external}@{~external}' '
+	git rev-parse bar@{~external}@{~external} >actual &&
+	git rev-parse zoo/zoo/bar >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success 'ref@{~mapping}' '
+	git config ref.mapping "!echo %ref%@{~external}@{~external}" &&
+	git rev-parse bar@{~mapping} >actual &&
+	git rev-parse zoo/zoo/bar >expected &&
+	test_cmp expected actual
+'
+
+test_done
-- 
1.7.3.3.476.g10a82