python subprocess to call git commands

Question

I am using a git command to get an ID from log history and then trying to pipe into into another command. The first one works fine but everything else is not. Here is my code:

import subprocess as sb
commit_id = sb.Popen(['git', 'merge-base' ,'FETCH_HEAD', 'HEAD'], stdout=sb.PIPE)
test=commit_id.communicate()[0]
print(test)
sb.Popen(['git' , 'diff' ,'--name-status' ,test, 'HEAD'])

It prints b'0bf694cea03670b318eeef8369dc0a0e0c761b29\n' and then gives an error.

Here is the error I am getting:

fatal: ambiguous argument '0bf694cea03670b318eeef8369dc0a0e0c761b29
': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]'

I'm not sure where I'm going wrong

Here are the git commands I am trying to implement. They work fine from Linux command line:

git merge-base FETCH_HEAD HEAD /this returns the commit id
git diff --name-status commit_id HEAD /this returns changed files
git diff --src-prefix 'Original:' --dst-prefix 'New:' commit_id filename /this returns lines changed in files

• Nicolas Martinez: I think this a git question, not a python one
• programminglearner: @NicolasMartinez not quite. the commands work fine as git commands. the issue is calling it from the script.
• s3dev: Is there a reason you’re using Python and not shell scripting?
• Nicolas Martinez: I see, have you tried removing last character of test? Maybe the newline is breaking it.
• kpie: As the answers state, the newline is breaking it.

Answer 1

Seems like the new line is not right, try:

sb.Popen(['git' , 'diff' ,'--name-status' ,test.strip(), 'HEAD'])

Answer 2

Your test variable has a trailing newline, strip it and it will work fine

import subprocess as sb
commit_id = sb.Popen(['git', 'merge-base' ,'FETCH_HEAD', 'HEAD'], stdout=sb.PIPE)
test=commit_id.communicate()[0]
print(test)
sb.Popen(['git' , 'diff' ,'--name-status' ,test[:-1], 'HEAD'])