upload: add a --topic option for setting topic explicitly

Let people specify the exact topic when uploading CLs.  The existing
-t option only supports setting the topic to the current local branch.

Add a --topic-branch long option to the existing -t to align it a bit
better with --hashtag & --hashtag-branch.

Change-Id: I010abc4a7f3c685021cae776dd1e597c22b79135
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/431997
Tested-by: Mike Frysinger <vapier@google.com>
Reviewed-by: Gavin Mak <gavinmak@google.com>
Commit-Queue: Mike Frysinger <vapier@google.com>

man/repo-upload.1

@@ -1,5 +1,5 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man.
-.TH REPO "1" "April 2024" "repo upload" "Repo Manual"
+.TH REPO "1" "June 2024" "repo upload" "Repo Manual"
 .SH NAME
 repo \- repo upload - manual page for repo upload
 .SH SYNOPSIS
@@ -18,8 +18,11 @@ show this help message and exit
 number of jobs to run in parallel (default: based on
 number of CPU cores)
 .TP
-\fB\-t\fR
-send local branch name to Gerrit Code Review
+\fB\-t\fR, \fB\-\-topic\-branch\fR
+set the topic to the local branch name
+.TP
+\fB\-\-topic\fR=\fI\,TOPIC\/\fR
+set topic for the change
 .TP
 \fB\-\-hashtag\fR=\fI\,HASHTAGS\/\fR, \fB\-\-ht\fR=\fI\,HASHTAGS\/\fR
 add hashtags (comma delimited) to the review