RFR: 1690: Make jcheck cli able to use conf from workspace or other commit [v3]

[Zhao Song]

On Wed, 30 Nov 2022 19:34:24 GMT, Zhao Song <zsong at openjdk.org> wrote:

>> Currently, the command `git skara jcheck` can only use the `.jcheck/conf` configuration file in the current checking commit.
>> However, sometimes users want to run jcheck with different configurations to validate their commits. Therefore, we need to upgrade `git skara jcheck`.
>> 
>> In this patch, `git skara jcheck` would be able to support following usecases.
>> 
>> 1. Run jcheck on a commit or a series of commits using the .jcheck/conf in the same commit. (what we do by default today)
>> `git skara jcheck`
>> 
>> 2. Run jcheck on a commit or a series of commits using the .jcheck/conf in a different specified commit. 
>> `git skara jcheck --specified-conf-commit <COMMIT HASH>`
>> 
>> 3. Run jcheck on a commit or a series of commits using the .jcheck/conf in my workspace. 
>> `git skara jcheck --workspace-conf`
>> 
>> 4. Run jcheck on a commit or a series of commits using a config file that I point to directly, that may have any name. 
>> `git skara jcheck --workspace-conf --conf-file <FILENAME>`
>> 
>> 5. Run jcheck on the diff in my current workspace, either --staged or not using the .jcheck/conf in my workspace.
>> `git skara jcheck --workspace-diff`
>
> Zhao Song has updated the pull request incrementally with one additional commit since the last revision:
> 
>   implemented case 5

vcs/src/main/java/org/openjdk/skara/vcs/git/GitRepository.java line 1699:

> 1697:                 author, ZonedDateTime.now(), List.of(""));
> 1698:         return new Commit(commitMetaData, List.of(diff(head())));
> 1699:     }

I tried to implement case 5 by Erik's idea. It seems work fine. But I don't know whether my implementation is acceptable, like the author and hash in the fake commit.

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PR: https://git.openjdk.org/skara/pull/1428