diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 28f61de9..a65078f7 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -129,7 +129,7 @@ jobs:
         id: changed-files-specific-source-file
         uses: ./
         with:
-          files-from-source-file: |
+          files_from_source_file: |
             test/changed-files-list.txt
             test/changed-files-list.txt
           files: |
@@ -152,7 +152,7 @@ jobs:
         id: changed-files-specific-comma-source-file
         uses: ./
         with:
-          files-from-source-file: |
+          files_from_source_file: |
             test/changed-files-list.txt
           separator: ","
       - name: Verify any_changed files comma separator
@@ -179,3 +179,22 @@ jobs:
           echo "${{ toJSON(steps.changed-files-custom-sha.outputs) }}"
         shell:
           bash
+      - name: Get branch name
+        id: branch-name
+        uses: tj-actions/branch-names@v4.5
+      - uses: nrwl/last-successful-commit-action@v1
+        id: last_successful_commit
+        with:
+          branch: ${{ steps.branch-name.outputs.base_ref_branch }}
+          workflow_id: 'test.yml'
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+      - name: Run changed-files with a custom base sha
+        id: changed-files-custom-base-sha
+        uses: ./
+        with:
+          base_sha: ${{ steps.last_successful_commit.outputs.commit_hash }}
+      - name: Show output
+        run: |
+          echo "${{ toJSON(steps.changed-files-custom-sha.outputs) }}"
+        shell:
+          bash
diff --git a/README.md b/README.md
index 410001d3..40c6a18e 100644
--- a/README.md
+++ b/README.md
@@ -98,8 +98,9 @@ jobs:
 | token         |  `string`   |    `false`    | `${{ github.token }}`         | [GITHUB_TOKEN](https://docs.github.com/en/free-pro-team@latest/actions/reference/authentication-in-a-workflow#using-the-github_token-in-a-workflow) <br /> or a repo scoped <br /> [Personal Access Token](https://docs.github.com/en/free-pro-team@latest/github/authenticating-to-github/creating-a-personal-access-token)              |
 | separator     |  `string`   |    `true`     | `' '`                         |  Output string separator   |
 | files         |  `string` OR `string[]` |   `false`  |                      | Check for changes  <br> using only these <br> list of file(s) <br> (Defaults to the <br> entire repo) |
+| base_sha           |  `string`      |    `false`     |                     | Specify a different <br> base commit SHA used <br> for comparing changes  |
 | sha           |  `string`      |    `true`     | `${{ github.sha }}`           | Specify a different <br> commit SHA used <br> for comparing changes  |
-| files-from-source-file |  `string`      |    `false`     |                    | Source file used populate <br>  the files input.  |
+| files_from_source_file |  `string`      |    `false`     |                    | Source file used populate <br>  the files input.  |
 
 ## Example
 
@@ -156,14 +157,14 @@ jobs:
         id: changed-files-specific-source-file
         uses: ./
         with:
-          files-from-source-file: |
+          files_from_source_file: |
             test/changed-files-list.txt
 
       - name: Use a source file or list of file(s) to populate to files input and optionally specify more files.
         id: changed-files-specific-source-file-and-specify-files
         uses: ./
         with:
-          files-from-source-file: |
+          files_from_source_file: |
             test/changed-files-list.txt
           files: |
             .github/workflows/rebase.yml
diff --git a/action.yml b/action.yml
index f19591d6..e9d3c199 100644
--- a/action.yml
+++ b/action.yml
@@ -10,7 +10,7 @@ inputs:
     description: 'Split character for array output'
     required: true
     default: " "
-  files-from-source-file:
+  files_from_source_file:
     description: 'Source file to populate the files input'
     required: false
     default: ""
@@ -19,9 +19,12 @@ inputs:
     required: false
     default: ""
   sha:
-    description: 'Specify a different commit SHA used for comparing changes'
+    description: 'Specify a current commit SHA used for comparing changes'
     required: true
     default: ${{ github.sha }}
+  base_sha:
+    description: 'Specify a base commit SHA on used for comparing changes'
+    required: false
 
 outputs:
   added_files:
@@ -76,7 +79,7 @@ runs:
       shell: bash
       env:
         INPUT_FILES: ${{ inputs.files }}
-        INPUT_FILES_FROM_SOURCE_FILE: ${{ inputs.files-from-source-file }}
+        INPUT_FILES_FROM_SOURCE_FILE: ${{ inputs.files_from_source_file }}
     - run: |
         bash $GITHUB_ACTION_PATH/entrypoint.sh
       id: changed-files
@@ -87,6 +90,7 @@ runs:
         # INPUT_<VARIABLE_NAME> is not available in Composite run steps
         # https://github.community/t/input-variable-name-is-not-available-in-composite-run-steps/127611
         INPUT_SHA: ${{ inputs.sha }}
+        INPUT_BASE_SHA: ${{ inputs.base_sha }}
         INPUT_TOKEN: ${{ inputs.token }}
         INPUT_FILES: ${{ join(format('{0} {1}', inputs.files, steps.source-input-files.outputs.files), ' ') }}
         INPUT_SEPARATOR: ${{ inputs.separator }}
diff --git a/entrypoint.sh b/entrypoint.sh
index 57759ee8..db26ceed 100755
--- a/entrypoint.sh
+++ b/entrypoint.sh
@@ -9,9 +9,9 @@ git remote set-url origin "https://${INPUT_TOKEN}@github.com/${GITHUB_REPOSITORY
 echo "Getting HEAD info..."
 
 if [[ -z $INPUT_SHA ]]; then
-  CURR_SHA=$(git rev-parse HEAD 2>&1) && exit_status=$? || exit_status=$?
+  CURRENT_SHA=$(git rev-parse HEAD 2>&1) && exit_status=$? || exit_status=$?
 else
-  CURR_SHA=$INPUT_SHA
+  CURRENT_SHA=$INPUT_SHA
 fi
 
 if [[ $exit_status -ne 0 ]]; then
@@ -20,7 +20,11 @@ if [[ $exit_status -ne 0 ]]; then
 fi
 
 if [[ -z $GITHUB_BASE_REF ]]; then
-  PREV_SHA=$(git rev-parse HEAD^1 2>&1) && exit_status=$? || exit_status=$?
+  if [[ -z $INPUT_BASE_SHA ]]; then
+    PREVIOUS_SHA=$(git rev-parse HEAD^1 2>&1) && exit_status=$? || exit_status=$?
+  else
+    PREVIOUS_SHA=$INPUT_BASE_SHA
+  fi
   TARGET_BRANCH=${GITHUB_REF/refs\/heads\//}
   CURRENT_BRANCH=$TARGET_BRANCH
   
@@ -30,10 +34,14 @@ if [[ -z $GITHUB_BASE_REF ]]; then
     exit 1
   fi
 else
-  TARGET_BRANCH=${GITHUB_BASE_REF}
+  TARGET_BRANCH=$GITHUB_BASE_REF
   CURRENT_BRANCH=$GITHUB_HEAD_REF
-  git fetch --depth=1 origin "${TARGET_BRANCH}":"${TARGET_BRANCH}"
-  PREV_SHA=$(git rev-parse "${TARGET_BRANCH}" 2>&1) && exit_status=$? || exit_status=$?
+  git fetch origin "${TARGET_BRANCH}":"${TARGET_BRANCH}"
+  if [[ -z $INPUT_BASE_SHA ]]; then
+    PREVIOUS_SHA=$(git rev-parse "${TARGET_BRANCH}" 2>&1) && exit_status=$? || exit_status=$?
+  else
+    PREVIOUS_SHA=$INPUT_BASE_SHA
+  fi
   
   if [[ $exit_status -ne 0 ]]; then
     echo "::warning::Unable to determine the base ref sha for ${TARGET_BRANCH}"
@@ -41,22 +49,22 @@ else
   fi
 fi
 
-echo "Retrieving changes between $PREV_SHA ($TARGET_BRANCH) → $CURR_SHA ($CURRENT_BRANCH)"
+echo "Retrieving changes between $PREVIOUS_SHA ($TARGET_BRANCH) → $CURRENT_SHA ($CURRENT_BRANCH)"
 
 UNIQUE_FILES=$(echo "$INPUT_FILES" | tr ' ' '\n' | sort -u | xargs)
 
 if [[ -z "$UNIQUE_FILES" ]]; then
   echo "Getting diff..."
-  ADDED=$(git diff --diff-filter=A --name-only "$PREV_SHA" "$CURR_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
-  COPIED=$(git diff --diff-filter=C --name-only "$PREV_SHA" "$CURR_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
-  DELETED=$(git diff --diff-filter=D --name-only "$PREV_SHA" "$CURR_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
-  MODIFIED=$(git diff --diff-filter=M --name-only "$PREV_SHA" "$CURR_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
-  RENAMED=$(git diff --diff-filter=R --name-only "$PREV_SHA" "$CURR_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
-  TYPE_CHANGED=$(git diff --diff-filter=T --name-only "$PREV_SHA" "$CURR_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
-  UNMERGED=$(git diff --diff-filter=U --name-only "$PREV_SHA" "$CURR_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
-  UNKNOWN=$(git diff --diff-filter=X --name-only "$PREV_SHA" "$CURR_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
-  ALL_CHANGED=$(git diff --diff-filter="*ACDMRTUX" --name-only "$PREV_SHA" "$CURR_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
-  ALL_MODIFIED_FILES=$(git diff --diff-filter="ACM" --name-only "$PREV_SHA" "$CURR_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
+  ADDED=$(git diff --diff-filter=A --name-only "$PREVIOUS_SHA" "$CURRENT_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
+  COPIED=$(git diff --diff-filter=C --name-only "$PREVIOUS_SHA" "$CURRENT_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
+  DELETED=$(git diff --diff-filter=D --name-only "$PREVIOUS_SHA" "$CURRENT_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
+  MODIFIED=$(git diff --diff-filter=M --name-only "$PREVIOUS_SHA" "$CURRENT_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
+  RENAMED=$(git diff --diff-filter=R --name-only "$PREVIOUS_SHA" "$CURRENT_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
+  TYPE_CHANGED=$(git diff --diff-filter=T --name-only "$PREVIOUS_SHA" "$CURRENT_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
+  UNMERGED=$(git diff --diff-filter=U --name-only "$PREVIOUS_SHA" "$CURRENT_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
+  UNKNOWN=$(git diff --diff-filter=X --name-only "$PREVIOUS_SHA" "$CURRENT_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
+  ALL_CHANGED=$(git diff --diff-filter="*ACDMRTUX" --name-only "$PREVIOUS_SHA" "$CURRENT_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
+  ALL_MODIFIED_FILES=$(git diff --diff-filter="ACM" --name-only "$PREVIOUS_SHA" "$CURRENT_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
 else
   ADDED_ARRAY=()
   COPIED_ARRAY=()
@@ -74,25 +82,25 @@ else
     echo "Checking for file changes: \"${path}\"..."
     IFS=" "
     # shellcheck disable=SC2207
-    ADDED_ARRAY+=($(git diff --diff-filter=A --name-only "$PREV_SHA" "$CURR_SHA" | grep -E "(${path})" | xargs || true))
+    ADDED_ARRAY+=($(git diff --diff-filter=A --name-only "$PREVIOUS_SHA" "$CURRENT_SHA" | grep -E "(${path})" | xargs || true))
     # shellcheck disable=SC2207
-    COPIED_ARRAY+=($(git diff --diff-filter=C --name-only "$PREV_SHA" "$CURR_SHA" | grep -E "(${path})" | xargs || true))
+    COPIED_ARRAY+=($(git diff --diff-filter=C --name-only "$PREVIOUS_SHA" "$CURRENT_SHA" | grep -E "(${path})" | xargs || true))
     # shellcheck disable=SC2207
-    DELETED_ARRAY+=($(git diff --diff-filter=D --name-only "$PREV_SHA" "$CURR_SHA" | grep -E "(${path})" | xargs || true))
+    DELETED_ARRAY+=($(git diff --diff-filter=D --name-only "$PREVIOUS_SHA" "$CURRENT_SHA" | grep -E "(${path})" | xargs || true))
     # shellcheck disable=SC2207
-    MODIFIED_ARRAY+=($(git diff --diff-filter=M --name-only "$PREV_SHA" "$CURR_SHA" | grep -E "(${path})" | xargs || true))
+    MODIFIED_ARRAY+=($(git diff --diff-filter=M --name-only "$PREVIOUS_SHA" "$CURRENT_SHA" | grep -E "(${path})" | xargs || true))
     # shellcheck disable=SC2207
-    RENAMED_ARRAY+=($(git diff --diff-filter=R --name-only "$PREV_SHA" "$CURR_SHA" | grep -E "(${path})" | xargs || true))
+    RENAMED_ARRAY+=($(git diff --diff-filter=R --name-only "$PREVIOUS_SHA" "$CURRENT_SHA" | grep -E "(${path})" | xargs || true))
     # shellcheck disable=SC2207
-    TYPE_CHANGED_ARRAY+=($(git diff --diff-filter=T --name-only "$PREV_SHA" "$CURR_SHA" | grep -E "(${path})" | xargs || true))
+    TYPE_CHANGED_ARRAY+=($(git diff --diff-filter=T --name-only "$PREVIOUS_SHA" "$CURRENT_SHA" | grep -E "(${path})" | xargs || true))
     # shellcheck disable=SC2207
-    UNMERGED_ARRAY+=($(git diff --diff-filter=U --name-only "$PREV_SHA" "$CURR_SHA" | grep -E "(${path})" | xargs || true))
+    UNMERGED_ARRAY+=($(git diff --diff-filter=U --name-only "$PREVIOUS_SHA" "$CURRENT_SHA" | grep -E "(${path})" | xargs || true))
     # shellcheck disable=SC2207
-    UNKNOWN_ARRAY+=($(git diff --diff-filter=X --name-only "$PREV_SHA" "$CURR_SHA" | grep -E "(${path})" | xargs || true))
+    UNKNOWN_ARRAY+=($(git diff --diff-filter=X --name-only "$PREVIOUS_SHA" "$CURRENT_SHA" | grep -E "(${path})" | xargs || true))
     # shellcheck disable=SC2207
-    ALL_CHANGED_ARRAY+=($(git diff --diff-filter="*ACDMRTUX" --name-only "$PREV_SHA" "$CURR_SHA" | grep -E "(${path})" | xargs || true))
+    ALL_CHANGED_ARRAY+=($(git diff --diff-filter="*ACDMRTUX" --name-only "$PREVIOUS_SHA" "$CURRENT_SHA" | grep -E "(${path})" | xargs || true))
     # shellcheck disable=SC2207
-    ALL_MODIFIED_FILES_ARRAY+=($(git diff --diff-filter="ACM" --name-only "$PREV_SHA" "$CURR_SHA" | grep -E "(${path})" | xargs || true))
+    ALL_MODIFIED_FILES_ARRAY+=($(git diff --diff-filter="ACM" --name-only "$PREVIOUS_SHA" "$CURRENT_SHA" | grep -E "(${path})" | xargs || true))
   done
 
   # shellcheck disable=SC2001