Suppress deletion in locked environment

[isc-vgao]

Testing Steps:

1. In Terminal/Windows Powershell, clone git-source-control repository and switch to testDelete branch

git clone git@github.com:intersystems/git-source-control.git

(enter passcode for deploy key if prompted)

cd git-source-control
git checkout suppressDelete

In IRIS terminal
2. Load git-source-control repository into IRIS from the community package registry.

zpm "install git-source-control"

3. Configure settings by running the following method and answering the prompts:

zpm "q"
d ##class(SourceControl.Git.API).Configure()

4. Load git-source-control into the current namespace

zpm "load <path to local git-source-control repo cloned in step 1>"

5. Open Studio
   If you see "Dubious Ownership" error in Output window, you have to change owner of local git-source-control repo. Steps to do that on Windows:
   1. Open Windows Powershell as Administrator
   2. Run
      a. $objSID = New-Object System.Security.Principal.SecurityIdentifier("<SID>")
      Note: replace <SID> with <SID> in "the current user is: '<SID>'" part of dubious ownership error message
      b. $objUser = $objSID.Translate([System.Security.Principal.NTAccount])
      c. icacls <path to local git-source-control repo cloned in step 1> /setowner $objUser.value /T
      Note: replace <path to local git-source-control repo cloned in step 1> with a path like C:\Users<your username>\
   3. Close and reopen Studio
6. Lock the environment

d ##class(SourceControl.Git.API).Lock()

7. In Studio's Workspace window Namespace tab, click Classes > SourceControl > Git > TestDelete.cls
8. Right-click on TestDelete and then click "Delete Class 'SourceControl.Git.TestDelete'" An error message should pop up with message "Can't delete in locked environment"
9. Open git-source-control repo in VS Code.

In VS Code,
10. Click the ObjectScript icon in the left side menu to open ObjectScript Explorer window, click "Choose Server and Namespace" and sign in using InterSystems Server Credentials.
11. Open an InterSystems Websocket Terminal.
12. Verify that you are still in locked environment

w ##class(SourceControl.Git.Utils).Locked()

should print 1
13. In ObjectScript Explorer window, click Classes > SourceControl > Git > TestDelete.cls
14. Right-click on TestDelete and then click "Delete" > "Confirm". Verify that TestDelete file wasn't deleted.

[isc-pbarton]

Functionality looks great. I would say that the SourceControl.Git.TestDelete class should be deleted entirely, since its only purpose is for manual testing of this change.

[isc-tleavitt]

Need to update CHANGELOG.md with a note about this in the "Fixed" section

[isc-tleavitt]

This fixes #302