[BUG] Unable to fetch file changes on merge event

[okamosy]

Is there an existing issue for this?

• I have searched the existing issues

Does this issue exist in the latest version?

• I'm using the latest release

Describe the bug?

When using this action to generate a list of changed folders, it fails to set the hashes correctly on a merge event. I get the following error: Similar commit hashes detected: previous sha: df2be13f61f134c597730151b8282627c4341643 is equivalent to the current sha: df2be13f61f134c597730151b8282627c4341643

To Reproduce

I've created a simple repo to test this. It can be forked here: https://github.com/okamosy/gha-test

The workflow in this only triggers on pull_request events

1. Create a new branch
2. Modify one or more of the readmes scattered throughout the project
3. Push the branch and raise a pr
4. Once the running action is complete, merge the PR
5. Examine the triggered action

What OS are you seeing the problem on?

ubuntu-latest or ubuntu-20.04

Expected behavior?

I would expect a list of modified folders to be displayed in the output step as is seen when the action runs when the PR is raised.

Relevant log output

# "Set base sha..."
  if [[ -n "" ]]; then
    BASE_SHA=$(git log --format="%H" --date=local --since="" --reverse | head -n 1)
    echo "::set-output name=base_sha::$BASE_SHA"
  elif [[ -n "" ]]; then
    echo "::set-output name=base_sha::"
  elif [[ "false" == "true" && "" == "true" && "" != "0000000000000000000000000000000000000000" ]]; then
    LAST_REMOTE_COMMIT=$(git rev-parse $(git branch -r --sort=-committerdate | head -1))
    if [[ "8c40a3b020d8e4f5885e97b71425e51ed72ee282" != "$LAST_REMOTE_COMMIT" ]]; then
      echo "::set-output name=base_sha::$LAST_REMOTE_COMMIT"
    fi
  elif [[ "false" == "true" && "" != "true" && "" != "0000000000000000000000000000000000000000" ]]; then
    echo "::set-output name=base_sha::"
  fi
  shell: /usr/bin/bash --noprofile --norc -e -o pipefail {0}
##[debug]/usr/bin/bash --noprofile --norc -e -o pipefail /home/runner/work/_temp/01f3a1f2-6041-491c-986a-95667575aba4.sh
##[debug]Finished: run
##[debug]Evaluating condition for step: 'run'
##[debug]Evaluating: success()
##[debug]Evaluating success:
##[debug]=> true
##[debug]Result: true
##[debug]Starting: run
##[debug]Loading inputs
##[debug]Evaluating: format('# "Set the sha..."
##[debug]if [[ -n "{0}" ]]; then
##[debug]  SHA=$(git log -1 --format="%H" --date=local --until="{1}")
##[debug]  echo "::set-output name=sha::$SHA"
##[debug]else
##[debug]  echo "::set-output name=sha::{2}"
##[debug]fi
##[debug]', inputs.until, inputs.until, inputs.sha)
##[debug]Evaluating format:
##[debug]..Evaluating String:
##[debug]..=> '# "Set the sha..."
##[debug]if [[ -n "{0}" ]]; then
##[debug]  SHA=$(git log -1 --format="%H" --date=local --until="{1}")
##[debug]  echo "::set-output name=sha::$SHA"
##[debug]else
##[debug]  echo "::set-output name=sha::{2}"
##[debug]fi
##[debug]'
##[debug]..Evaluating Index:
##[debug]....Evaluating inputs:
##[debug]....=> Object
##[debug]....Evaluating String:
##[debug]....=> 'until'
##[debug]..=> ''
##[debug]..Evaluating Index:
##[debug]....Evaluating inputs:
##[debug]....=> Object
##[debug]..Evaluating String:
##[debug]..=> 'sha'
##[debug]=> '8c40a3b020d8e4f5885e97b71425e51ed72ee282'
##[debug]Result: '8c40a3b020d8e4f5885e97b71425e51ed72ee282'
##[debug]Evaluating: steps.base-sha.outputs.base_sha
##[debug]Evaluating Index:
##[debug]..Evaluating Index:
##[debug]....Evaluating Index:
##[debug]......Evaluating steps:
##[debug]......=> Object
##[debug]......Evaluating String:
##[debug]......=> 'base-sha'
##[debug]....=> Object
##[debug]....Evaluating String:
##[debug]....=> 'outputs'
##[debug]..=> Object
##[debug]..Evaluating String:
##[debug]..=> 'base_sha'
##[debug]=> null
##[debug]Result: null
##[debug]Evaluating: inputs.path
##[debug]Evaluating Index:
##[debug]..Evaluating inputs:
##[debug]..=> Object
##[debug]..Evaluating String:
##[debug]..=> 'path'
##[debug]=> '.'
##[debug]Result: '.'
##[debug]Evaluating: inputs.use_fork_point
##[debug]Evaluating Index:
##[debug]..Evaluating inputs:
##[debug]..=> Object
##[debug]..Evaluating String:
##[debug]..=> 'use_fork_point'
##[debug]=> 'false'
##[debug]Result: 'false'
##[debug]Evaluating condition for step: 'run'
##[debug]Evaluating: success()
##[debug]Evaluating success:
##[debug]=> true
##[debug]Result: true
##[debug]Starting: run
##[debug]Loading inputs
##[debug]Loading env
Run # "Calculating the previous and current SHA..."
  # "Calculating the previous and current SHA..."
  bash $GITHUB_ACTION_PATH/diff-sha.sh
  shell: /usr/bin/bash --noprofile --norc -e -o pipefail {0}
  env:
    GITHUB_SERVER_URL: https://github.com
    GITHUB_REPOSITORY: okamosy/gha-test
    GITHUB_BASE_REF: main
    GITHUB_HEAD_REF: test-2
    GITHUB_ACTION_PATH: /home/runner/work/_actions/tj-actions/changed-files/v29.0.3
    GITHUB_WORKSPACE: /home/runner/work/gha-test/gha-test
    INPUT_SHA: 8c40a3b020d8e4f5885e97b71425e51ed72ee282
    INPUT_BASE_SHA: 
    INPUT_PATH: .
    INPUT_USE_FORK_POINT: false
##[debug]/usr/bin/bash --noprofile --norc -e -o pipefail /home/runner/work/_temp/928fbc2d-a1b2-4a3f-828d-ae1873f9faee.sh
::group::changed-files-diff-sha
changed-files-diff-sha
  ##[debug]Resolving repository path: /home/runner/work/gha-test/gha-test/.
  Verifying git version...
  Valid git version found: (2.37.3)
  ##[debug]Getting HEAD SHA...
  ##[debug]Verifying the current commit SHA: 8c40a3b020d8e4f5885e97b71425e51ed72ee282
  ##[debug]Current SHA: 8c40a3b020d8e4f5885e97b71425e51ed72ee282
  ##[debug]GITHUB_BASE_REF: main...
  remote: Total 0 (delta 0), reused 0 (delta 0), pack-reused 0        
  ##[debug]Previous SHA: 8c40a3b020d8e4f5885e97b71425e51ed72ee282
  ##[debug]Verifying the previous commit SHA: 8c40a3b020d8e4f5885e97b71425e51ed72ee282
  Error: Similar commit hashes detected: previous sha: 8c40a3b020d8e4f5885e97b71425e51ed72ee282 is equivalent to the current sha: 8c40a3b020d8e4f5885e97b71425e51ed72ee282
  Error: You seem to be missing 'fetch-depth: 0' or 'fetch-depth: 2'. See https://github.com/tj-actions/changed-files#usage
  Error: Process completed with exit code 1.

Anything else?

No response

Code of Conduct

• I agree to follow this project's Code of Conduct

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