feat: support partial clone on Git repository

[RShirohara]

Description

Add partial clone support to Git repository. (Resolves #370)

Suggestion

Add --partial option to ghq get for partial clone.
The --partial option can specify either blobless or treeless, and each corresponding to the --filter option in git clone.

• blobless: --filter=blob:none
• treeless: --filter=tree:0

Example

In blobless clone:

ghq get --partial blobless github.com/x-motemen/ghq

In treeless clone:

ghq get --partial treeless github.com/x-motemen/ghq

[Copilot]

Pull Request Overview

This PR adds support for partial cloning of Git repositories by introducing a new "--partial" flag that accepts either "blobless" or "treeless", and implements the corresponding filter options in the clone command.

• Added a new "partial" flag in commands.go with validation.
• Updated clone logic in vcs.go to incorporate filter options for partial clones.
• Expanded test coverage for the new partial clone functionality in cmd_get_test.go, vcs_test.go, commands_test.go, and getter.go.

Reviewed Changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
commands.go	Added a new flag for partial clones with validation.
cmd_get_test.go	Added test cases for blobless, treeless, and invalid partial options.
vcs.go	Implemented filter options based on partial flag values.
vcs_test.go	Added tests to verify partial clone filter flags in git commands.
commands_test.go	Updated clone argument structure to include the partial flag.
getter.go	Propagated the partial option to the repository getter.
cmd_get.go	Passed the partial flag from CLI to the clone options.

Comments suppressed due to low confidence (1)

commands.go:48

• [nitpick] Consider including the allowed values in the error message for improved clarity, e.g., "flag partial value "%v" is not allowed; allowed values are 'blobless' or 'treeless'".

return fmt.Errorf("flag partial value \"%v\" is not allowed", v)

[RShirohara]

@Songmu

All checks have been completed and there appear to be no review comments by Copilot.
Are there any items that I need to address?

[Songmu]

@RShirohara

Thank you. I think this is a very good pull request.

However, while "blobless" and "treeless" are well-known idioms, I'm not sure whether it's okay to take them as arguments as they are. Do you know of any other tools that take arguments like that?

If there are no other tools with such an argument system, I think it would be good to add a --filter option to ghq clone similar to git, and pass it through to the git command. It would be a raw interface, though.

[RShirohara]

@Songmu

Thank you. I was not able to take into account the implementation trends of other commands......

blobless and treeless were used because, like the already supported --shallow option (which will eventually be converted to --depth=1), we wanted to "support commands defined in Git in a more straightforward syntax".

For other common Git helpers, I investigated support for the --filter option on clone command and found the following results:

• cli/cli
  • Can put Git options directly after --.
• mislav/hub
  • Not supported?

It will not be consistent with the existing --shallow command, but we will try again to add the --filter option as you commented.

[Songmu]

You're right, it's not consistent with the shallow command... I'm starting to think it's OK as it is.

[Songmu]

OK. I would like to accept your original changes. Sorry for the confusion. @RShirohara

[RShirohara]

@Songmu

There was a conflict, which has been resolved, and i have confirmed that all unit tests pass on local.

[RShirohara]

Thank you!