[arch-general] Why no git --depth=1 option for makepkg?

[Eli Schwartz]

On 03/03/2018 12:50 PM, Jonathon Fernyhough wrote:
> On 03/03/18 08:48, mike lojkovic via arch-general wrote:
>> It would be extremely nice to have shallow clone support for some packages.
>> The Unreal git repo requires pulling down 20 gigabytes for a build, taking
>> maybe a half hour each time.
>>
> 
> An effective workaround is to create a shallow clone prior to running
> makepkg,
> 
> $ cd $SRCDEST
> $ git clone --bare --depth=1 https://github.com/cisco/ChezScheme.git
> ChezScheme
> $ cd ChezScheme
> $ git config remote.origin.fetch "+refs/*:refs/*"
> 
> and away you go.
> 
> However.
> 
> You can't just use --depth=1 on everything without running into "weird"
> problems. For example, any VCS package that relies on tags for its
> pkgver will fail to find the last tagged commit, and so the fetch depth
> must be increased to extend to the tagged commit.

Yep -- more or less this. There is no way for git to fetch "all commits
since a given tag", and obviously `git describe` which is used in the
standard pkgver() function cannot describe the remote repository... not
to mention what happens when the repository has *no* tags, and git
rev-list --count HEAD depends on all commits since the repository was
initialized.

Then there is the fact that --depth, or even --single-branch (not that
this usually saves much space or time), will break on PKGBUILDs that use
`git cherry-pick` to backport fixes (more commonly seen in non-VCS
packages obviously).

All in all, there is simply no way to generically support shallow clones
in a generic way. The best you can do is take a given PKGBUILD, predict
what it needs, and perform the clone manually according to handpicked
criteria as makepkg will detect that clone and then simply fetch new
changes which respects a previous shallow clone designation.

-- 
Eli Schwartz
Bug Wrangler and Trusted User

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