On 04/28/2014 01:03 AM, Johan Herland wrote:
On Sun, Apr 27, 2014 at 7:38 PM, Jeremy Morton <ad...@game-point.net> wrote:
On 27/04/2014 10:09, Johan Herland wrote:
On Sun, Apr 27, 2014 at 1:56 AM, Jeremy Morton<ad...@game-point.net>
wrote:
Currently, git records a checksum, author, commit date/time, and commit
message with every commit (as get be seen from 'git log').  I think it
would
be useful if, along with the Author and Date, git recorded the name of
the
current branch on each commit.


This has been discussed multiple times in the past. One example here:
http://thread.gmane.org/gmane.comp.version-control.git/229422

I believe the current conclusion (if any) is that encoding such
information as a _structural_ part of the commit object is not useful.
See the old thread(s) for the actual pro/con arguments.

As far as I can tell from that discussion, the general opposition to
encoding the branch name as a structural part of the commit object is that,
for some people's workflows, it would be unhelpful and/or misleading. Well
fair enough then - why don't we make it a setting that is off by default,
and can easily be switched on?  That way the people for whom tagging the
branch name would be useful have a very easy way to switch it on.

Obviously, the feature would necessarily have to be optional, simply
because Git would have to keep understanding the old commit object
format for a LONG time (probably indefinitely), and there's nothing
you can do to prevent others from creating old-style commit objects.

Which brings us to another big con at this point: The cost of changing
the commit object format. One can argue for or against a new commit
object format, but the simple truth at this point is that changing the
structure of the commit object is expensive. Even if we were all in
agreement about the change (and so far we are not), there are multiple
Git implementations (libgit2, jgit, dulwich, etc.) that would all have
to learn the new commit object, not to mention that bumping
core.repositoryformatversion would probably make your git repo
incompatible with a huge number of existing deployments for the
foreseeable future.

Therefore, the most pragmatic and constructive thing to do at this
point, is IMHO to work within the confines of the existing commit
object structure. I actually believe using commit message trailers
like "Made-on-branch: frotz" in addition to some helpful
infrastructure (hooks, templates, git-interpret-trailers, etc.) should
get you pretty much exactly what you want. And if this feature turns
out to be extremely useful for a lot of users, we can certainly
consider changing the commit object format in the future.

I know
that for the workflows I personally have used in the past, such tagging
would be very useful.  Quite often I have been looking through the Git log
and wondered what feature a commit was "part of", because I have feature
branches.  Just knowing that branch name would be really useful, but the
branch has since been deleted... and in the case of a ff-merge (which I
thought was recommended in Git if possible), the branch name is completely
gone.

True. The branch name is - for better or worse - simply not considered
very important by Git, and a Git commit is simply not considered (by
Git at least) to "be part of" or otherwise "belong to" any branch.
Instead the commit history/graph is what Git considers important, and
the branch names are really just more-or-less ephemeral pointers into
that graph.

AFAIK, recording the current branch name in commits was not considered
to the worth including in Linus' original design, and since then it
seems to only have come up a few times on the mailing list. This is
quite central to Git's design, and changing it at this point should
not be done lightly.

IINM, Mercurial does this differently, so that may be a better fit for
the workflows where keeping track of branch names is very important.

That said, you are of course free to add this information to your own
commit messages, by appending something like "Made-on-branch: frotz".
In a company setting, you can even create a commit message template or
(prepare-)commit-msg hook to have this line created automatically for
you and your co-workers. You could even append such information
retroactively to existing commits with "git notes". There is also the
current interpret-trailers effort by Christian Couder [1] that should
be useful in creating and managing such lines.

[1]: http://thread.gmane.org/gmane.comp.version-control.git/245874

Well I guess that's another way of doing it.  So, why aren't Author and Date
trailers?  They don't seem any more fundamental to me than branch name.  I
mean the only checkin information you really *need* is the checksum, and
commit's parents.  The Author and Date are just extra pieces of information
you might find useful sometimes, right?  A bit like some people might find
branch checkin name useful sometimes...?

Yeah, sure. Author and Date (and Committer, for that matter) is just
metadata, and the current branch name is simply just another kind of
metadata. All of them are more-or-less free-form text fields, and off

no they're not.  In strictly controlled environments they form part of
the audit record for the source code.

Yes they can be faked (explicitly), but -- again in strictly controlled
environments -- that can be limited to "before it was first pushed".
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