diff --git a/README.md b/README.md
index 9782376..7787919 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@ An action with forks in mind! Automatically sync a branch on your fork with the
 
 **Bonus:** This action can also sync between branches on any two repositories. So you have options. :slightly_smiling_face:
 
-**\*\*FIXED in v3.1:\*\*** Git config values are now set only if they haven't been set elsewhere by other actions in a workflow. This was done to avoid conflict setting config values in other job steps (like [gpg commit signing](https://github.com/aormsby/Fork-Sync-With-Upstream-action/wiki/GPG-Signing))
+**\*\*FIXED in v3.2:\*\*** Checking for new commits to sync has been improved to better support active development branches. Instead of only comparing head SHA values, it does a deeper hash comparison between the target and upstream branches since the last action run. Length of time is based on new input var `shallow_since`, which defaults to `1 month ago`. ([wiki](https://github.com/aormsby/Fork-Sync-With-Upstream-action/wiki/Configuration#advanced-use))
 
 **\*\*NEW in v3:\*\*** Test Mode runs key checks on your input values to help you verify your action configuration before running and avoid errors when you go live! ([wiki](https://github.com/aormsby/Fork-Sync-With-Upstream-action/wiki#test-mode))
 
@@ -47,16 +47,19 @@ This action supports syncing from both public and private upstream repos. Store
 
 #### Advanced Use (all optional args)
 
-| Name                        |     Required?      | Default                     | Example                    |
-| --------------------------- | :----------------: | --------------------------- | -------------------------- |
-| host_domain                 | :white_check_mark: | 'github.com'                | 'github.com'               |
-| target_branch_checkout_args |                    |                             | '--recurse-submodules'     |
-| git_log_format_args         |                    | '--pretty=oneline'          | '--graph --pretty=oneline' |
-| upstream_pull_args          |                    |                             | '--ff-only --tags'         |
-| target_branch_push_args     |                    |                             | '--force'                  |
-| git_config_user             |                    | 'GH Action - Upstream Sync' |                            |
-| git_config_email            |                    | 'action@github.com'         |                            |
-| git_config_pull_rebase      |                    | 'false'                     |                            |
+| Name                        |     Required?      | Default                     | Example                             |
+| --------------------------- | :----------------: | --------------------------- | ----------------------------------- |
+| host_domain                 | :white_check_mark: | 'github.com'                | 'github.com'                        |
+| shallow_since               | :white_check_mark: | '1 month ago'               | '2 days ago', '3 weeks 7 hours ago' |
+| target_branch_checkout_args |                    |                             | '--recurse-submodules'              |
+| git_log_format_args         |                    | '--pretty=oneline'          | '--graph --pretty=oneline'          |
+| upstream_pull_args          |                    |                             | '--ff-only --tags'                  |
+| target_branch_push_args     |                    |                             | '--force'                           |
+| git_config_user             |                    | 'GH Action - Upstream Sync' |                                     |
+| git_config_email            |                    | 'action@github.com'         |                                     |
+| git_config_pull_rebase      |                    | 'false'                     |                                     |
+
+`shallow_since` -> Value should match the time between workflow runs to get the history depth required (but no more) for a good check of new commits to sync
 
 ##### Git Config Settings
 
@@ -75,6 +78,8 @@ Want more output variables? [Open an issue](https://github.com/aormsby/Fork-Sync
 ## Sample Workflow
 
 ```yaml
+name: 'Usptream Sync'
+
 on:
   schedule:
     - cron:  '0 7 * * 1,4'
@@ -103,7 +108,7 @@ jobs:
     # Step 2: run the sync action
     - name: Sync upstream changes
       id: sync
-      uses: aormsby/Fork-Sync-With-Upstream-action@v3.1
+      uses: aormsby/Fork-Sync-With-Upstream-action@v3.2
       with:
         target_sync_branch: my-branch
         # REQUIRED 'target_repo_token' exactly like this!
diff --git a/action.yaml b/action.yaml
index 948569b..6ab3a8a 100644
--- a/action.yaml
+++ b/action.yaml
@@ -72,6 +72,11 @@ inputs:
     required: true
     default: 'github.com'
 
+  shallow_since:
+    description: 'Length of time used when fetching shallow repo data, should match how often you perform a sync'
+    required: true
+    default: '1 month ago'
+
 outputs:
   has_new_commits:
     description: 'true when new commits were included in this sync'
diff --git a/entry/run_action.sh b/entry/run_action.sh
index e4f2917..e923215 100755
--- a/entry/run_action.sh
+++ b/entry/run_action.sh
@@ -1,30 +1,27 @@
 #!/bin/sh
 
+# shellcheck disable=SC1091
 # source action scripts, then run individual functions
 
-# shellcheck disable=SC1091
 # config git settings
 . "${ACTION_PARENT_DIR}"/run/config_git.sh
 config_for_action
 
-# shellcheck disable=SC1091
 # checkout target branch in target repo
 . "${ACTION_PARENT_DIR}"/run/checkout_branch.sh
 checkout
 
-# shellcheck disable=SC1091
 # set upstream repo
 . "${ACTION_PARENT_DIR}"/run/set_upstream_repo.sh
 set_upstream
 
-# shellcheck disable=SC1091
 # check for new commits and sync or exit
 . "${ACTION_PARENT_DIR}"/run/get_updates.sh
 check_for_updates
+find_last_synced_commit
 output_new_commit_list
 sync_new_commits
 
-# shellcheck disable=SC1091
 # push newly synced commits to local branch
 . "${ACTION_PARENT_DIR}"/run/push_updates.sh
 push_new_commits
diff --git a/run/get_updates.sh b/run/get_updates.sh
index d7568b9..feff8ae 100644
--- a/run/get_updates.sh
+++ b/run/get_updates.sh
@@ -1,19 +1,30 @@
 #!/bin/sh
 
-# check latest commit hashes for a match, exit if nothing to sync
+# shellcheck disable=SC2086
 
+# check latest commit hashes for a match, exit if nothing to sync
 check_for_updates() {
     write_out -1 'Checking for new commits on upstream branch.\n'
 
-    # get latest commit hashes from local and remote branches for comparison
-    # shellcheck disable=SC2086
-    git fetch upstream "${INPUT_UPSTREAM_SYNC_BRANCH}"
-    LOCAL_COMMIT_HASH=$(git rev-parse "${INPUT_TARGET_SYNC_BRANCH}")
+    # fetch commits from upstream branch within given time frame (default 1 month)
+    git fetch --quiet --shallow-since="${INPUT_SHALLOW_SINCE}" upstream "${INPUT_UPSTREAM_SYNC_BRANCH}"
+    COMMAND_STATUS=$?
+
+    if [ "${COMMAND_STATUS}" != 0 ]; then
+        # if shallow fetch fails, no new commits are avilable for sync
+        HAS_NEW_COMMITS=false
+        exit_no_commits
+    fi
+
     UPSTREAM_COMMIT_HASH=$(git rev-parse "upstream/${INPUT_UPSTREAM_SYNC_BRANCH}")
 
-    if [ -z "${LOCAL_COMMIT_HASH}" ] || [ -z "${UPSTREAM_COMMIT_HASH}" ]; then
+    # check is latest upstream hash is in target branch
+    git fetch --quiet --shallow-since="${INPUT_SHALLOW_SINCE}" origin "${INPUT_TARGET_SYNC_BRANCH}"
+    BRANCH_WITH_LATEST="$(git branch "${INPUT_TARGET_SYNC_BRANCH}" --contains="${UPSTREAM_COMMIT_HASH}")"
+
+    if [ -z "${UPSTREAM_COMMIT_HASH}" ]; then
         HAS_NEW_COMMITS="error"
-    elif [ "${LOCAL_COMMIT_HASH}" = "${UPSTREAM_COMMIT_HASH}" ]; then
+    elif [ -n "${BRANCH_WITH_LATEST}" ]; then
         HAS_NEW_COMMITS=false
     else
         HAS_NEW_COMMITS=true
@@ -34,20 +45,43 @@ exit_no_commits() {
     write_out 0 'No new commits to sync. Finishing sync action gracefully.'
 }
 
+find_last_synced_commit() {
+    LAST_SYNCED_COMMIT=""
+    TARGET_BRANCH_LOG="$(git rev-list "${INPUT_TARGET_SYNC_BRANCH}")"
+    UPSTREAM_BRANCH_LOG="$(git rev-list "upstream/${INPUT_UPSTREAM_SYNC_BRANCH}")"
+
+    for hash in ${TARGET_BRANCH_LOG}; do
+        UPSTREAM_CHECK="$(echo "${UPSTREAM_BRANCH_LOG}" | grep "${hash}")"
+        if [ -n "${UPSTREAM_CHECK}" ]; then
+            LAST_SYNCED_COMMIT="${hash}"
+            break
+        fi
+    done
+}
+
 # display new commits since last sync
 output_new_commit_list() {
-    write_out -1 '\nNew commits since last sync:'
-    # shellcheck disable=SC2086
-    git log upstream/"${INPUT_UPSTREAM_SYNC_BRANCH}" "${LOCAL_COMMIT_HASH}"..HEAD ${INPUT_GIT_LOG_FORMAT_ARGS}
+    if [ -z "${LAST_SYNCED_COMMIT}" ]; then
+        write_out -1 "\nNo previous sync found from upstream repo. Syncing entire commit history."
+        UNSHALLOW=true
+    else
+        write_out -1 '\nNew commits since last sync:'
+        git log upstream/"${INPUT_UPSTREAM_SYNC_BRANCH}" "${LAST_SYNCED_COMMIT}"..HEAD ${INPUT_GIT_LOG_FORMAT_ARGS}
+    fi
 }
 
 # sync from upstream to target_sync_branch
 sync_new_commits() {
     write_out -1 '\nSyncing new commits...'
 
-    # pull_args examples: "--ff-only", "--tags", "--ff-only --tags"
-    # shellcheck disable=SC2086
-    git pull --no-edit ${INPUT_UPSTREAM_PULL_ARGS} upstream "${INPUT_UPSTREAM_SYNC_BRANCH}"
+    if [ "${UNSHALLOW}" = true ]; then
+        git repack -d upstream "${INPUT_UPSTREAM_SYNC_BRANCH}"
+        git pull --unshallow --no-edit ${INPUT_UPSTREAM_PULL_ARGS} upstream "${INPUT_UPSTREAM_SYNC_BRANCH}"
+    else
+        # pull_args examples: "--ff-only", "--tags", "--ff-only --tags"
+        git pull --no-edit ${INPUT_UPSTREAM_PULL_ARGS} upstream "${INPUT_UPSTREAM_SYNC_BRANCH}"
+    fi
+
     COMMAND_STATUS=$?
 
     if [ "${COMMAND_STATUS}" != 0 ]; then