scm: history does not work when using builtin vscode extensions

[vince-fugnitto]

Bug Description:

The scm-history view does not work when using the vscode builtin extensions, there is a message stating that history does not work for git source control (the same is true when an individual file is selected to display it's history):

Steps to Reproduce:

1. remove @theia/git from the example application(s)

2. use the git builtins (tested with 1.53.2):

   "vscode-git": "https://open-vsx.org/api/vscode/git/1.53.2/file/vscode.git-1.53.2.vsix",
   "vscode-git-ui": "https://open-vsx.org/api/vscode/git-ui/1.53.2/file/vscode.git-ui-1.53.2.vsix"

3. start the application with a folder that is under version control

4. confirm that version control works (scm-view), but not the history view

[vince-fugnitto]

It looks like it was never actually supported #6381, the vscode api for extensions does not provide history, but it does provide timeline information. I believe it was the reason to have some @theia/scm-extra (which I had forgotten about).

@msujew I believe there is no issue, if we use the builtin we should not use @theia/git or @theia/scm-extra.

[danepowell]

if we use the builtin we should not use @theia/git or @theia/scm-extra

Since the Theia Blueprint uses the builtin Git extension instead of @theia/git, does that mean it should remove @theia/scm and @theia/scm-extra? I'm happy to open a PR if so.

[vince-fugnitto]

Since the Theia Blueprint uses the builtin Git extension instead of @theia/git, does that mean it should remove @theia/scm and @theia/scm-extra? I'm happy to open a PR if so.

@danepowell @theia/scm is necessary is necessary for source-control support in which vscode.git is a contribution. The @theia/scm-extra can be safely removed I believe as it only contributes the history-view at this time.

[danepowell]

Thanks; PR to remove scm-extra: eclipse-theia/theia-ide#293