git-codereview: new sync-branch and related fixes

This CL adds a new command, "git codereview sync-branch",
which does the appropriate git merge for the current branch.

This CL also fixes a bug in "git codereview branchpoint",
and therefore also commands like "git codereview pending",
which was getting the branchpoint wrong for merges,
with the effect that a merge showed too many pending CLs.

This CL also fixes a bug in "git codereview change", which was
formerly willing to run "git checkout" with a pending merge,
which had the effect of flattening the merge mysteriously.
Now it detects the merge and refuses to run.

All of this should make merges easier and less error-prone
as we use dev branches more often.

With the earlier CL in this stack that allows working directly
on local branches, this is now a great way to run a merge
updating dev.regabi:

	git change dev.regabi
	git sync-branch

(with appropriate aliases to avoid typing "codereview").

Fixes golang/go#26201.

Change-Id: Ic24603123ca5135a72004309f5bb208ff149c9eb
Reviewed-on: https://go-review.googlesource.com/c/review/+/279772
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/git-codereview/pending.go b/git-codereview/pending.go
index c1594b5..f3e3369 100644
--- a/git-codereview/pending.go
+++ b/git-codereview/pending.go
@@ -293,6 +293,9 @@ func cmdPending(args []string) {
 // commit and its Gerrit state.
 func formatCommit(w io.Writer, c *Commit, short bool) {
 	g := c.g
+	if g == nil {
+		g = new(GerritChange)
+	}
 	msg := strings.TrimRight(c.Message, "\r\n")
 	fmt.Fprintf(w, "%s", c.ShortHash)
 	var tags []string
@@ -318,6 +321,9 @@ func formatCommit(w io.Writer, c *Commit, short bool) {
 	case "ABANDONED":
 		tags = append(tags, "abandoned")
 	}
+	if c.Merge != "" {
+		tags = append(tags, "merge="+c.Merge[:7])
+	}
 	if len(tags) > 0 {
 		fmt.Fprintf(w, " (%s)", strings.Join(tags, ", "))
 	}