Re: [PATCH] builtin/remote.c: show progress when renaming remote references

> When renaming a remote, Git needs to rename all remote tracking
> references to the remote's new name (e.g., renaming
> "refs/remotes/old/foo" to "refs/remotes/new/foo" when renaming a remote
> from "old" to "new").
> 
> This can be somewhat slow when there are many references to rename,
> since each rename is done in a separate call to rename_ref() as opposed
> to grouping all renames together into the same transaction. It would be
> nice to execute all renames as a single transaction, but there is a
> snag: the reference transaction backend doesn't support renames during a
> transaction (only individually, via rename_ref()).
> 
> The reasons there are described in more detail in [1], but the main
> problem is that in order to preserve the existing reflog, it must be
> moved while holding both locks (i.e., on "oldname" and "newname"), and
> the ref transaction code doesn't support inserting arbitrary actions
> into the middle of a transaction like that.
> 
> As an aside, adding support for this to the ref transaction code is
> less straightforward than inserting both a ref_update() and ref_delete()
> call into the same transaction. rename_ref()'s special handling to
> detect D/F conflicts would need to be rewritten for the transaction code
> if we wanted to proactively catch D/F conflicts when renaming a
> reference during a transaction. The reftable backend could support this
> much more readily because of its lack of D/F conflicts.
> 
> Instead of a more complex modification to the ref transaction code,
> display a progress meter when running verbosely in order to convince the
> user that Git is doing work while renaming a remote.
> 
> This is mostly done as-expected, with the minor caveat that we
> intentionally count symrefs renames twice, since renaming a symref takes
> place over two separate calls (one to delete the old one, and another to
> create the new one).
> 
> [1]: https://lore.kernel.org/git/572367B4.4050207@alum.mit.edu/
> 
> Suggested-by: brian m. carlson <sandals@crustytoothpaste.net>
> Signed-off-by: Taylor Blau <me@ttaylorr.com>