upload: Support Update-Pr-Body as a commit tag

This allows you to manually specify one or more prs
as no-update while maintaining the default option for
all other prs. (and vise versa)

Fixes: #140

docs/upload.md

@@ -82,6 +82,13 @@ branches once they are merged. If a relative branch is specified, only one
 "Branch:" can be specified and all relative topics must specify the same
 relative branch (or none, in which case it will get set automatically).
 
+**Update-Pr-Body:**
+: When set to true (default) revup will attempt to update the github PR body
+whenever the local version has changes. When set to false, revup will create
+PRs with the commit text to start out, but does not attempt to update it again.
+This allows users to use the github UI to edit the PR body without having
+revup overwrite those changes.
+
 For each review, the pull request title is the title of the first commit
 message in that topic, and the body is the body text of the first commit
 message in that topic. A user can also create an empty commit if they
@@ -149,13 +156,9 @@ confirmation step and only print topic info.
 : Print out status info of pull requests for existing topics but don't attempt
 to push or update them.
 
-**--no-update-pr-body**
-: Revup will attempt to update the github PR body whenever the local version
-has changes that differ from the remote. However, this means that if a user
-uses the github web interface to edit the PR body, especially to embed
-HTML or images, revup won't know about it and will try to overwrite it on
-the next upload. With this flag, uploading will only update the pr body
-on creation, but not after, ensuring that any custom PR text is kept.
+**--update-pr-body**
+: Boolean that specifies how the pr body text is updated. See the
+Update-Pr-Body: tag section for details.
 
 **--review-graph**
 : Enable the review graph feature, which adds a comment containing links and
@@ -197,4 +200,4 @@ mappings are used to transform usernames specified in Reviewers/Assignees.
 If "a2r", add users from the Assignees tag as reviewers. If "both", do both of the previous.
 
 **--head**
-: The name or commit of the branch to be uploaded. If not specified, defaults to HEAD.
+: The name or commit of the branch to be uploaded. If not specified, defaults to HEAD.

revup/topic_stack.py

@@ -48,6 +48,7 @@ def format_remote_branch(uploader: str, base_branch: str, topic: str) -> str:
 TAG_RELATIVE = "relative"
 TAG_RELATIVE_BRANCH = "relative-branch"
 TAG_UPLOADER = "uploader"
+TAG_UPDATE_PR_BODY = "update-pr-body"
 VALID_TAGS = {
     TAG_BRANCH,
     TAG_LABEL,
@@ -57,6 +58,7 @@ def format_remote_branch(uploader: str, base_branch: str, topic: str) -> str:
     TAG_ASSIGNEE,
     TAG_TOPIC,
     TAG_UPLOADER,
+    TAG_UPDATE_PR_BODY,
 }
 
 RE_COMMIT_LABEL = re.compile(r"^(?P<label1>[a-zA-Z\-_0-9]+):.*|^\[(?P<label2>[a-zA-Z\-_0-9]+)\].*")
@@ -494,6 +496,14 @@ async def populate_reviews(
             if len(topic.tags[TAG_UPLOADER]) > 1:
                 raise RevupUsageException(f"Can't specify more than one uploader for topic {name}!")
 
+            if TAG_UPDATE_PR_BODY in topic.tags:
+                if len(topic.tags[TAG_UPDATE_PR_BODY]) > 1 or min(
+                    topic.tags[TAG_UPDATE_PR_BODY]
+                ).lower() not in {"true", "false"}:
+                    raise RevupUsageException(
+                        f"Invalid tags for update-pr-body: {topic.tags[TAG_UPDATE_PR_BODY]}"
+                    )
+
             relative_topic = ""
             if force_relative_chain and last_topic is not None:
                 relative_topic = last_topic
@@ -1055,7 +1065,7 @@ async def query_github(self) -> None:
 
     def populate_update_info(
         self,
-        update_pr_body: bool,
+        update_pr_body_arg: bool,
     ) -> None:
         """
         Populate information necessary to do PR creation / update in github.
@@ -1128,6 +1138,11 @@ def populate_update_info(
                     topic.tags[TAG_ASSIGNEE], self.names_to_logins
                 ).difference(review.pr_info.assignees)
 
+                if TAG_UPDATE_PR_BODY in topic.tags:
+                    update_pr_body = min(topic.tags[TAG_UPDATE_PR_BODY]).lower() == "true"
+                else:
+                    update_pr_body = update_pr_body_arg
+
                 if review.pr_info.baseRef != review.remote_base:
                     review.pr_update.baseRef = review.remote_base
                 if update_pr_body and review.pr_info.body != body: