Setup user agent and config to run proof builds.
If working copy is a "detached HEAD" then proof build fails with the following error
17:03:51,926 ERROR - fatal: ambiguous argument 'origin/master..(detached from 0a75bb3)': unknown revision or path not in the working tree.
17:03:51,926 ERROR - Use '--' to separate paths from revisions, like this:
17:03:51,926 ERROR - 'git <command> [<revision>...] -- [<file>...]'
17:03:51,764 INFO - Executing post-execute action...
17:03:51,764 ERROR - Step 'master>checkout repo>checkout Git' is failed: Failed to run command: git log --name-status --pretty=raw --reverse "origin/master..(detached from 0a75bb3)"
Command return code: 128
Command error output: fatal: ambiguous argument 'origin/master..(detached from 0a75bb3)': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]'

Obviously, the reason for this QB executes `git branch` command to get current SHA-1 to get changes between origin/master and current commit.
Here is an appropriate log cut:
17:03:49,954 INFO - Getting local change...
17:03:49,980 INFO - Checking working branch...
17:03:50,188 DEBUG - Executing command: git branch
17:03:50,188 DEBUG - Command working directory: d:\AShu\projects\1C-Mirror
17:03:50,246 INFO - * (detached from 0a75bb3)
17:03:50,246 INFO - dUnit
17:03:50,246 INFO - db-export-powershell
17:03:50,246 INFO - err-580-service
17:03:50,246 INFO - fpc
17:03:50,246 INFO - master

But current commit is not always a named branch, e.g. we want to test several previous commit(s) in our test branch.

I expect QB wouldn't fail to get changes between a current commit and an upstream branch.
I guess, `git rev-parse HEAD` is a more suitable command to get a current commit ID.