Re: [RFC] Proof of concept: Support multiple authors

Hi,

On Sun, Jan 29, 2017 at 7:06 PM, Cornelius Schumacher
[off-list ref] wrote:

This patch is a proof of concept implementation of support for
multiple authors. It adds an optional `authors` header to commits
which is set when there are authors configured in the git config.

I am just wondering if you have read and taken into account the
previous threads on this mailing list about the same subject, like for
example this one:

https://public-inbox.org/git/CAOvwQ4i_HL7XGnxZrVu3oSnsbnTyxbg8Vh6vzi4c1isSrrexYQ@mail.gmail.com/

A new command `git-authors` is used to manage the authors settings.
Authors are identified by initials and their names and emails are
set in a `.git_authors_map` file.

Signed-off-by: Cornelius Schumacher <redacted>
---

When doing pair programming we have to work around the limitation that
git can only have a single author in each commit. There are some tools
which help with that such as [git-duet] [1], but there are still some
limits, because the information about multiple authors is not reflected
in the native git data model.

Here is a proposal how to change that and implement native support for
multiple authors in git. It comes with a patch as a proof of concept.
The patch by no means is finished, it doesn't cover all cases and needs
more tests and error handling. It's meant as an illustration of the
concept.

The basic idea is to introduce a new optional `authors` header in
commits which contains a list of authors. The header is set in each new
commit when there is an entry `authors.current` in the git config listing
the current authors. When this config is not there the behavior falls
back to the current standard behavior.

When the header is there it is treated in the same way as the author
header. It's preserved on merges and similar operations, is displayed in
git show, and used to create a list of `From` addresses in `format-patch`.
Email supports multiple `From` addresses as specified in section 3.6.2 of
RFC 5322.

When multiple authors are configured, they still write the standard author
header to keep backwards compatibility. The first author is used as author
and committer. In the future it might be good to implement something like
automatic rotation of the order of authors to give credit in a fair way.

To make it easier to work with the authors there is a new command
`git-authors`. It sets the list of authors using initials as shortcut for
the full configuration with name and email. The mapping of initials to
names and email addresses is taken from a file `.git_authors_map` in the
home directory of the users. This way it's possible to quickly set a list
of authors by running a command such as `git authors ab cd`. This is
useful when doing pair programming because the people working together
usually switch quite frequently and using the command with the intials is
quicker and less error-prone than editing the configuration with full
names and emails.

The command also supports setting a single author, setting more than two
authors or clearing the configuration for multiple authors to go back to
the standard behavior without the new authors header.

The concept of the command and the mappings file is similar to what
git-duet does, so that it should be familiar to many people doing pair
programming. The behavior of git doesn't change when the new feature is
not used and when it's used it should be backwards compatible so that it
doesn't break existing functionality. This should make a smooth transition
for users who choose to make use of it.

Adding support for multiple authors would make the life of developers doing
pair programming easier. It would be useful in itself, but it would also
need support by other tools around git to use its full potential.

From what I recall from previous discussions, the most important
question is: are you sure that it doesn't break any other tool?

This
might take a while, but I think it's worth the effort.

I'm willing to continue to work on this and create a patch which is suitable
for inclusion in git.