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, 3 insertions, 0 deletions

diff --git a/git-codereview/review.go b/git-codereview/review.go
index 0deb039..5c7f16d 100644
--- a/git-codereview/review.go
+++ b/git-codereview/review.go
@@ -67,6 +67,7 @@ Available commands:
 	rebase-work
 	submit [-i | commit...]
 	sync
+	sync-branch [-continue]
 
 See https://pkg.go.dev/golang.org/x/review/git-codereview
 for the full details of each command.
@@ -112,6 +113,8 @@ func main() {
 		cmd = cmdSubmit
 	case "sync":
 		cmd = cmdSync
+	case "sync-branch":
+		cmd = cmdSyncBranch
 	case "test-loadAuth": // for testing only.
 		cmd = func([]string) { loadAuth() }
 	}