[PATCH 2/7] sha1_name: factor out die_no_upstream()

[Ramkumar Ramachandra <artagnon@gmail.com>]

Currently interpret_branch_name() tries to parse various things, and
finally falls back to parsing <branch>@{u[pstream]}.  It dies if the
input string contained an "@{u[pstream]}" but an upstream could not be
found.  The logic can be generalized to check for any branch property
after branch_get().  In preparation for introducing more special @{...}
forms, factor out die_no_upstream().

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
---
 sha1_name.c | 40 ++++++++++++++++++++++------------------
 1 file changed, 22 insertions(+), 18 deletions(-)

diff --git a/sha1_name.c b/sha1_name.c
index 766e4e9..7aabd94 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -998,6 +998,24 @@ int get_sha1_mb(const char *name, unsigned char *sha1)
 	return st;
 }
 
+static void die_no_upstream(struct branch *upstream, char *name) {
+	/*
+	 * Upstream can be NULL only if cp refers to HEAD and HEAD
+	 * points to something different than a branch.
+	 */
+	if (!upstream)
+		die(_("HEAD does not point to a branch"));
+	if (!upstream->merge || !upstream->merge[0]->dst) {
+		if (!ref_exists(upstream->refname))
+			die(_("No such branch: '%s'"), name);
+		if (!upstream->merge)
+			die(_("No upstream configured for branch '%s'"),
+				upstream->name);
+		die(_("Upstream branch '%s' not stored as a remote-tracking branch"),
+			upstream->merge[0]->src);
+	}
+}
+
 /*
  * 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
@@ -1022,7 +1040,7 @@ int get_sha1_mb(const char *name, unsigned char *sha1)
 int interpret_branch_name(const char *name, struct strbuf *buf)
 {
 	char *cp;
-	struct branch *upstream;
+	struct branch *branch;
 	int namelen = strlen(name);
 	int len = interpret_nth_prior_checkout(name, buf);
 	int tmp_len;
@@ -1059,24 +1077,10 @@ int interpret_branch_name(const char *name, struct strbuf *buf)
 		return -1;
 	len = cp + tmp_len - name;
 	cp = xstrndup(name, cp - name);
-	upstream = branch_get(*cp ? cp : NULL);
-	/*
-	 * Upstream can be NULL only if cp refers to HEAD and HEAD
-	 * points to something different than a branch.
-	 */
-	if (!upstream)
-		die(_("HEAD does not point to a branch"));
-	if (!upstream->merge || !upstream->merge[0]->dst) {
-		if (!ref_exists(upstream->refname))
-			die(_("No such branch: '%s'"), cp);
-		if (!upstream->merge)
-			die(_("No upstream configured for branch '%s'"),
-				upstream->name);
-		die(_("Upstream branch '%s' not stored as a remote-tracking branch"),
-			upstream->merge[0]->src);
-	}
+	branch = branch_get(*cp ? cp : NULL);
+	die_no_upstream(branch, cp);
 	free(cp);
-	cp = shorten_unambiguous_ref(upstream->merge[0]->dst, 0);
+	cp = shorten_unambiguous_ref(branch->merge[0]->dst, 0);
 	strbuf_reset(buf);
 	strbuf_addstr(buf, cp);
 	free(cp);
-- 
1.8.3.rc3.17.gd95ec6c.dirty