Re: [PATCH v5 00/12] rebase: update branches in multi-part topic

>
> This series is based on ds/branch-checked-out.
>
> This is a feature I've wanted for quite a while. When working on the sparse
> index topic, I created a long RFC that actually broke into three topics for
> full review upstream. These topics were sequential, so any feedback on an
> earlier one required updates to the later ones. I would work on the full
> feature and use interactive rebase to update the full list of commits.
> However, I would need to update the branches pointing to those sub-topics.
>
> This series adds a new --update-refs option to 'git rebase' (along with a
> rebase.updateRefs config option) that adds 'update-ref' commands into the
> TODO list. This is powered by the commit decoration machinery.
>
> As an example, here is my in-progress bundle URI RFC split into subtopics as
> they appear during the TODO list of a git rebase -i --update-refs:
>
> pick 2d966282ff3 docs: document bundle URI standard
> pick 31396e9171a remote-curl: add 'get' capability
> pick 54c6ab70f67 bundle-uri: create basic file-copy logic
> pick 96cb2e35af1 bundle-uri: add support for http(s):// and file://
> pick 6adaf842684 fetch: add --bundle-uri option
> pick 6c5840ed77e fetch: add 'refs/bundle/' to log.excludeDecoration
> update-ref refs/heads/bundle-redo/fetch
>
> pick 1e3f6546632 clone: add --bundle-uri option
> pick 9e4a6fe9b68 clone: --bundle-uri cannot be combined with --depth
> update-ref refs/heads/bundle-redo/clone
>
> pick 5451cb6599c bundle-uri: create bundle_list struct and helpers
> pick 3029c3aca15 bundle-uri: create base key-value pair parsing
> pick a8b2de79ce8 bundle-uri: create "key=value" line parsing
> pick 92625a47673 bundle-uri: unit test "key=value" parsing
> pick a8616af4dc2 bundle-uri: limit recursion depth for bundle lists
> pick 9d6809a8d53 bundle-uri: parse bundle list in config format
> pick 287a732b54c bundle-uri: fetch a list of bundles
> update-ref refs/heads/bundle-redo/list
>
> pick b09f8226185 protocol v2: add server-side "bundle-uri" skeleton
> pick 520204dcd1c bundle-uri client: add minimal NOOP client
> pick 62e8b457b48 bundle-uri client: add "git ls-remote-bundle-uri"
> pick 00eae925043 bundle-uri: serve URI advertisement from bundle.* config
> pick 4277440a250 bundle-uri client: add boolean transfer.bundleURI setting
> pick caf4599a81d bundle-uri: allow relative URLs in bundle lists
> pick df255000b7e bundle-uri: download bundles from an advertised list
> pick d71beabf199 clone: unbundle the advertised bundles
> pick c9578391976 t5601: basic bundle URI tests
> # Ref refs/heads/bundle-redo/rfc-3 checked out at '/home/stolee/_git/git-bundles'
>
> update-ref refs/heads/bundle-redo/advertise
>
>
> Here is an outline of the series:
>
>  * Patch 1 updates some tests for branch_checked_out() to use 'git bisect'
>    and 'git rebase' as black-boxes instead of manually editing files inside
>    $GIT_DIR. (Thanks, Junio!)
>  * Patch 2 updates some tests for branch_checked_out() for the 'apply'
>    backend.
>  * Patch 3 updates branch_checked_out() to parse the
>    rebase-merge/update-refs file to block concurrent ref updates and
>    checkouts on branches selected by --update-refs.
>  * Patch 4 updates the todo list documentation to remove some unnecessary
>    dots in the 'merge' command. This makes it consistent with the 'fixup'
>    command before we document the 'update-ref' command.
>  * Patch 5 updates the definition of todo_command_info to use enum values as
>    array indices.
>  * Patches 6-8 implement the --update-refs logic itself.
>  * Patch 9 specifically updates the update-refs file every time the user
>    edits the todo-list (Thanks Phillip!)
>  * Patch 10 adds the rebase.updateRefs config option similar to
>    rebase.autoSquash.
>  * Patch 11 ignores the HEAD ref when creating the todo list instead of
>    making a comment (Thanks Elijah!)
>  * Patch 12 adds messaging to the end of the rebase stating which refs were
>    updated (Thanks Elijah!)
>
> During review, we have identified some areas that would be good for
> #leftoverbits:
>
>  * Warn the user when they add an 'update-ref ' command but is checked out
>    in another worktree.
>  * The checks in patch 9 are quadratic. They could be sped up using
>    hashtables.
>  * Consider whether we should include an 'update-ref ' command for the HEAD
>    ref, so that all refs are updated in the same way. This might help
>    confused users.

>  * The error message for failed ref updates could include information on the
>    commit IDs that would have been used. This can help the user fix the
>    situation by updating the refs manually.
>  * Modify the --update-refs option from a boolean to an
>    optionally-string-parameter that specifies refspecs for the 'update-ref'
>    commands.

> Updates in v5
> =============
>
>  * Rename 'wt_dir' to 'wt_git_dir' for clarity.
>  * The documented behavior around 'fixup!' and 'squash!' commits was
>    incorrect, so update the commit message, documentation, and test to
>    demonstrate the actual behavior.
>  * Use CALLOC_ARRAY() to be more idiomatic.
>  * Be much more careful about propagating errors.
>  * Commit message typo: "We an" to "We can"
>  * Remove unnecessary null OID check when writing refs, since those would
>    already be removed by a previous step.