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

[Zhao Song]

On Tue, 29 Nov 2022 18:24:50 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`

I still have two questions.

1. For point 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.", currently, I think in most cases it will be used with point 3. So in my implementation, user could only point a config file with any name in workspace.

If needed, I can make user be able to point any file in any commit as the configuration file.

2. For point 5, to run jcheck on the diff in workspace, I don't have some good ideas. So I just commit the changes temporarily and then reset the head after running jcheck. But it will make user's staged changes to be unstaged.

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