upload: Add "branch-format" config option and commit tag

Branch-format will let you control how branches are named,
which has an effect on when branches collide. This can be
set on cmdline, from config file, or on a topic-by-topic
basis inside the commit text.

user+branch is the default today and will remain the default.
Branch names will never collide if using this, but you cannot
retarget to other base branches, and you must use Uploader: if
another user wants to push to this branch.

user allows retargeting prs to other base branches, but will
not allow multiple base-branches to be specified. if they are,
it will warn to specify user+branch instead.

branch will allow others to upload to the same pr, but uploader:
cannot be used.

none includes both limitations and features of user and branch.

I don't really believe there's good use cases for branch and none,
but i'm implementing them to be complete.

revup/revup.py

@@ -272,6 +272,9 @@ async def main() -> int:
         "--user-aliases",
     )
     upload_parser.add_argument("--uploader")
+    upload_parser.add_argument(
+        "--branch_format", choices=["user+branch", "user", "branch", "none"], default="user+branch"
+    )
     upload_parser.add_argument("--pre-upload", "-p")
     upload_parser.add_argument("--relative-chain", "-c", action="store_true")
     upload_parser.add_argument("--auto-topic", "-a", action="store_true")

revup/topic_stack.py

@@ -28,14 +28,23 @@
 # https://docs.github.com/en/get-started/using-git/dealing-with-special-characters-in-branch-and-tag-names
 RE_BRANCH_ALLOWED = re.compile(r"^[\w\d_\.\/-]+$")
 
+BRANCH_FORMAT_STRATEGIES = {
+    "user+branch": "{uploader}/revup/{base_branch}/{topic}",
+    "user": "{uploader}/revup/{topic}",
+    "branch": "revup/{base_branch}/{topic}",
+    "none": "revup/{topic}",
+}
+
 
-def format_remote_branch(uploader: str, base_branch: str, topic: str) -> str:
+def format_remote_branch(uploader: str, base_branch: str, topic: str, branch_format: str) -> str:
     """
     Branches are named so that it is clear that they are made by revup
     and can be force pushed at any time, and to minimize collision with
     manually created branches.
     """
-    return f"{uploader}/revup/{base_branch}/{topic}"
+    return BRANCH_FORMAT_STRATEGIES[branch_format].format(
+        uploader=uploader, base_branch=base_branch, topic=topic
+    )
 
 
 RE_TAGS = re.compile(r"^(?P<tagname>[a-zA-Z\-]+):(?P<tagvalue>.*)$", re.MULTILINE)
@@ -49,6 +58,7 @@ def format_remote_branch(uploader: str, base_branch: str, topic: str) -> str:
 TAG_RELATIVE_BRANCH = "relative-branch"
 TAG_UPLOADER = "uploader"
 TAG_UPDATE_PR_BODY = "update-pr-body"
+TAG_BRANCH_FORMAT = "branch-format"
 VALID_TAGS = {
     TAG_BRANCH,
     TAG_LABEL,
@@ -59,6 +69,7 @@ def format_remote_branch(uploader: str, base_branch: str, topic: str) -> str:
     TAG_TOPIC,
     TAG_UPLOADER,
     TAG_UPDATE_PR_BODY,
+    TAG_BRANCH_FORMAT,
 }
 
 RE_COMMIT_LABEL = re.compile(r"^(?P<label1>[a-zA-Z\-_0-9]+):.*|^\[(?P<label2>[a-zA-Z\-_0-9]+)\].*")
@@ -504,6 +515,15 @@ async def populate_reviews(
                         f"Invalid tags for update-pr-body: {topic.tags[TAG_UPDATE_PR_BODY]}"
                     )
 
+            if TAG_BRANCH_FORMAT in topic.tags:
+                if (
+                    len(topic.tags[TAG_BRANCH_FORMAT]) > 1
+                    or min(topic.tags[TAG_BRANCH_FORMAT]).lower() not in BRANCH_FORMAT_STRATEGIES
+                ):
+                    raise RevupUsageException(
+                        f"Invalid tags for branch-format: {topic.tags[TAG_BRANCH_FORMAT]}"
+                    )
+
             relative_topic = ""
             if force_relative_chain and last_topic is not None:
                 relative_topic = last_topic
@@ -573,7 +593,7 @@ async def populate_reviews(
                 if name not in self.topics:
                     logging.warning(f"Couldn't find any topic named {name}")
 
-    async def populate_relative_reviews(self, uploader: str) -> None:
+    async def populate_relative_reviews(self, uploader: str, branch_format: str) -> None:
         for name, topic in self.topological_topics():
             if topic.relative_topic:
                 if len(topic.tags[TAG_BRANCH]) == 0:
@@ -638,7 +658,16 @@ async def populate_relative_reviews(self, uploader: str) -> None:
                     f" {topic.relative_topic.tags[TAG_UPLOADER] or '{}'}"
                 )
             topic_uploader = min(topic.tags[TAG_UPLOADER]) if topic.tags[TAG_UPLOADER] else uploader
-
+            topic_branch_format = (
+                min(topic.tags[TAG_BRANCH_FORMAT]).lower()
+                if TAG_BRANCH_FORMAT in topic.tags
+                else branch_format
+            )
+            if "branch" not in topic_branch_format and len(topic.tags[TAG_BRANCH]) > 1:
+                raise RevupUsageException(
+                    "Cannot use multiple branches if Branch-Format: does not "
+                    'include "branch", try overriding it for this topic'
+                )
             for branch in topic.tags[TAG_BRANCH]:
                 review = Review(topic)
                 # Track whether we need to query for the relative pr
@@ -663,7 +692,9 @@ async def populate_relative_reviews(self, uploader: str) -> None:
                         review.base_ref = await self.git_ctx.to_commit_hash(relative_branch)
                     review.remote_base = self.git_ctx.remove_branch_prefix(relative_branch)
 
-                review.remote_head = format_remote_branch(topic_uploader, base_branch, name)
+                review.remote_head = format_remote_branch(
+                    topic_uploader, base_branch, name, topic_branch_format
+                )
 
                 topic.reviews[branch] = review
 

revup/upload.py

@@ -43,6 +43,7 @@ async def main(
         )
         await topics.populate_relative_reviews(
             args.uploader if args.uploader else git_ctx.author,
+            branch_format=args.branch_format,
         )
 
     if not args.dry_run: