On Tue, Mar 13 2018, Michal Novotny jotted:
> On Tue, Mar 13, 2018 at 10:07 AM, Ævar Arnfjörð Bjarmason
> <avarab@xxxxxxxxx> wrote:
>>
>> On Tue, Mar 13 2018, Michal Novotny jotted:
>>
>>> Hello,
>>>
>>> currently, if I try to create a tag that has tilde "~" in name, an
>>> error is raised. E.g.
>>>
>>> $ git tag rpkg-util-1.4~rc1
>>> fatal: 'rpkg-util-1.4~rc1' is not a valid tag name.
>>>
>>> Now, actually it would be very cool if tilde was allowed in a tag name
>>> because we would like to use it for tagging pre-releases of (not-only
>>> rpm) packages.
>>>
>>> Is there some deep technical reason why tilde cannot be present in a
>>> tag name? I tried that e.g.
>>
>> Yes, because a trailing tilde is part of git's rev syntax, see "man
>> git-rev-parse", or try in any repo:
>>
>> git show HEAD
>> git show HEAD~2
>> git show HEAD^~2
>
> Right, reading the man pages:
>
> <rev>~<n>, e.g. master~3
> A suffix ~<n> to a revision parameter means the commit
> object that is the <n>th generation ancestor of the named commit
> object, following only the first
> parents. I.e. <rev>~3 is equivalent to <rev>^^^ which is
> equivalent to <rev>^1^1^1. See below for an illustration of the usage
> of this form.
>
> Would it be acceptable to disallow only ~<n> (<n> as [0-9]+) in a tag
> name but allow ~[^0-9].*, i.e. if the immediately following symbol
> after '~' is a letter, do not
> interpret ~ as a special character. Could it work?
We could make that work, with some caveats:
1) The syntax we've reserved for refnames is quite small, and my bias
at least would be to say you should just make a tag like
rpkg-util-1.4-rc1 instead (as e.g. git.git and linux.git do).
Carving out an exception like this also means we couldn't use
~[^0-9].* for anything magical in the future.
But I think that's a rather small objection, we have other syntax
escape hatches, and we're unlikely to use ~[^0-9].* as some new
magic.
2) If we patch git to accept this, you'll be creating refs that aren't
inter-operable with previous versions of git.
This is a big deal. E.g. you'll happily create this special ref,
then try to push it to github, and they'll croak because that's an
invalid ref to them. Ditto some co-worker of yours who's using an
older version of git.
FWIW if you manually create such a tag e.g. for-each-ref will emit
'warning: ignoring ref with broken name' and just not show it.
>>
>> etc.
>>
>> Although I guess git could learn to disambiguate that form from the tag
>> you're trying to create.
>>
>>> git tag rpkg-util-1.4%rc1
>>>
>>> but percentage sign does not seem to be particular fitting for
>>> pre-release marking.
>>>
>>> Thank you
>>> clime
