bug#37189: 25.4.1: vc-hg-ignore implementation is missing

[Wolfgang Scherer]

Am 22.02.20 um 20:30 schrieb Dmitry Gutov:
> On 22.02.2020 0:22, Wolfgang Scherer wrote:
>> Both use cases are important for casual users of a VC. Before this
>> research, I did not know anything about SVN, SRC, Bzr, Mtn. Ignore file
>> support in 'vc' as a distilled experience cache does come in handy,
>> even for experienced users. Especially, if escaping/anchoring is
>> implemented.
>
> Escaping/anchoring can be added in the next step of the "series of ad-hoc 
> patches".
I'm not saying to implement it now, I am just describing use cases, which are 
not limited to Emacs 27.
>> RCS, SCCS do not have ignore files, so they should error out. SRC has
>> ignore files similar to CVS and SVN.
>
> They will fail anyway because they implement neither 'find-ignore-file' nor 
> the 'ignore' backend actions.
This is in reference to the condition-case around find-ignore-file, which is 
not necessary. It is OK to error out in that case.
>
>> Do not forget that CVS and SVN
>> have functions vc-cvs-ignore and vc-svn-ignore, which are called
>> *instead*  of vc-default-ignore. I.e. The changes to vc-default-ignore
>> do not affect those VCs. For the invocation of find-ignore-file in
>> vc-ignore, see below.
>
> I think the patch is compatible with those. At least with the SVN one 
> (vc-cvs-ignore might need a little work).
>
> Have you tried this patch with SVN? Is there a particular scenario where it 
> fails?
No, it should not. CVS is now also patched, so it will no longer fail.
>
>>> Roughly and handwavy, we can take this case to mean "use default-directory".
>> Unfortunately not. If the file or pattern to be ignored is in a
>> subdirectory of default-directory, the DIRECTORY argument must reflect
>> this for CVS, SVN, SRC.
>
> vc-svn-ignore looks like it can handle either calling convention.
As does vc-cvs-ignore. So, for right now, it is OK.
>
>> I apologize for introducing ewoc into vc-dir-mode. Meanwhile I have
>> discovered vc-deduce-fileset, which does all the hard work for
>> preparing a fileset in vc-dir-mode, dired-mode and other
>> modes. vc-deduce-fileset delivers a backend and absolute file names,
>> not relative file names.
>
> Please submit a patch fixing that whenever you have the time.
I don't think it should be done before Emacs 28.
>
>> I think introducing relative file names in
>> function APIs is the wrong way to go. However, as a preliminary
>> solution, it does suffice.
>
> I think it's just fine if the function is supposed to receive an *ignore 
> pattern*, and not a simple file name.

Again, it is probably not the time right now to discuss these matters.

What will be the time frame for starting Emacs 28 topics?