Re: feature/package+vc 04c4c578c7 3/4: Allow for packages to be installed directly from VCS

[Stefan Monnier]

Philip Kaludercic [2022-10-30 14:15:07] wrote:
> Stefan Monnier <monnier@iro.umontreal.ca> writes:
>>> I guess so.  Here is a possible patch that should behave close enough to
>>> elpa-admin.el using "blame"
>>
>> Why do you use `blame` rather than `log` like `elpa-admin.el`?
>
> I tried to use log like in elpa-admin.el, but the issue was I had to
> either
>
> 1. Define the generic interface to search for a line using a regular
>    expression that is not an Elisp regular expression, and could
>    conceivably differ between different VCS that might also implement
>    'last-change'.
>
> 2. Deal with the issue that the Version header might move between
>    revisions, meaning that a line range wouldn't do a good job at
>    capturing the right commit.

FWIW, I suspect that your `git blame` will give the same answer as the
corresponding `git log` (it will probably end up using the same code
under the hood), but I don't understand what you mean above.  I think
`git log` would accept the exact same `-L` as you use for `git blame`
and will deal with "the issue that the Version header might move" in the
exact same way.

>> Hmm... the code I see in your patch uses `vc-region-history` (which is
>> only supported for Git and Hg, currently, and is fairly difficult to
>> support in a generic way) rather than `vc-annotate`.
>> Am I missing something?
>
> Uh, that is my mistake.  I started writing that code yesterday (I
> believe?) and simply forgot what I had used.  I'll try to translate that
> into vc-annotate before pushing anything.

[ Just to be clear, I wasn't implying a preference between `vc-annotate`
  and `vc-region-history`.  As fallback, they both seem fine to me.  ]

> Checking out a specific revision is currently only done right after
> cloning, so this is always a reset.  The issue here is that I am trying
> to stay generic and was using 'vc-retrieve-tag' (but perhaps
> 'vc-checkout' would be better), so this is an issue that might have to
> be tackled in vc-git.el...

I find this part of VC beyond repair: AFAICT the notion of
"tag/snapshot/..."  has been defined "on the fly" with a narrow view of
what was needed for one particular situation at a particular time.

It's probably worth "throwing it out" (well, keeping it on life support)
and introducing a whole new set of operations based on a design that
tries to accommodate all the various related notions out there.


        Stefan