Github plugin installation fails

[vinokurig]

Describe the bug

Github plugin installation fails, Git extension fails as well if the GitHub plugin is turned on.
This happens because the GitHub plugin has vscode git extension in it's plugin dependencies. Since eclipse-theia/theia@2d4c845 was merged Theia automatically installs dependent plugins, but the vscode git extension is not located in the vscode marketplace.

Che version

• latest
• nightly
• other: please specify

Steps to reproduce

1. Start a workspace with the GitHub plugin turned on.
   WRONG:
   Git plugin doesn't work:
   
   The error is shown in the log console:

root ERROR TypeError: Cannot read property 'versions' of undefined
    at Request._callback (/home/theia/node_modules/@theia/plugin-ext-vscode/lib/node/plugin-vscode-resolver.js:129:55)
    at Request.self.callback (/home/theia/node_modules/request/request.js:185:22)
    at Request.emit (events.js:198:13)
    at Request.<anonymous> (/home/theia/node_modules/request/request.js:1161:10)
    at Request.emit (events.js:198:13)
    at IncomingMessage.<anonymous> (/home/theia/node_modules/request/request.js:1083:12)
    at Object.onceWrapper (events.js:286:20)
    at IncomingMessage.emit (events.js:203:15)
    at endReadableNT (_stream_readable.js:1129:12)
    at process._tickCallback (internal/process/next_tick.js:63:19)
root ERROR Uncaught Exception:  Error: No extension
root ERROR Error: No extension
    at Request._callback (/home/theia/node_modules/@theia/plugin-ext-vscode/lib/node/plugin-vscode-resolver.js:120:44)
    at Request.self.callback (/home/theia/node_modules/request/request.js:185:22)
    at Request.emit (events.js:198:13)
    at Request.<anonymous> (/home/theia/node_modules/request/request.js:1161:10)
    at Request.emit (events.js:198:13)
    at IncomingMessage.<anonymous> (/home/theia/node_modules/request/request.js:1083:12)
    at Object.onceWrapper (events.js:286:20)
    at IncomingMessage.emit (events.js:203:15)
    at endReadableNT (_stream_readable.js:1129:12)
    at process._tickCallback (internal/process/next_tick.js:63:19)

Expected behavior

Runtime

• kubernetes (include output of kubectl version)
• Openshift (include output of oc version)
• minikube (include output of minikube version and kubectl version)
• minishift (include output of minishift version and oc version)
• docker-desktop + K8S (include output of docker version and kubectl version)
• other: (please specify)

Screenshots

Installation method

• chectl
• che-operator
• minishift-addon
• I don't know

Environment

• my computer
  • Windows
  • Linux
  • macOS
• Cloud
  • Amazon
  • Azure
  • GCE
  • other (please specify)
• other: please specify

Additional context

[tolusha]

eclipse-theia/theia#5993

[ibuziuk]

@vinokurig removing need-triage label, please set a milestone based on the team priorities

[ibuziuk]

oh, looks like it is part of #14295 - moving to 7.2.0