diff --git a/github_scripts/get_git_sources.py b/github_scripts/get_git_sources.py
index 323afbed..56681973 100644
--- a/github_scripts/get_git_sources.py
+++ b/github_scripts/get_git_sources.py
@@ -3,9 +3,8 @@
 # The file LICENCE, distributed with this code, contains details of the terms
 # under which the code may be used.
 # -----------------------------------------------------------------------------
-
 """
-Clone sources for a rose-stem run for use with git bdiff module in scripts
+Helper functions for cloning git sources in command line builds
 """
 
 import re
@@ -19,6 +18,28 @@
 logger = logging.getLogger(__name__)
 
 
+def get_source(
+    source: str,
+    ref: str,
+    dest: Path,
+    repo: str,
+    use_mirrors: bool = False,
+    mirror_loc: Path = Path(""),
+) -> None:
+
+    if ".git" in source:
+        if use_mirrors:
+            mirror_loc = Path(mirror_loc) / "MetOffice" / repo
+            print(f"Cloning/Updating {repo} from mirror {mirror_loc} at ref {ref}")
+            clone_repo_mirror(source, ref, repo, mirror_loc, dest)
+        else:
+            print(f"Cloning/Updating {repo} from {source} at ref {ref}")
+            clone_repo(source, ref, dest)
+    else:
+        print(f"Syncing {repo} at ref {ref}")
+        sync_repo(source, ref, dest)
+
+
 def run_command(
     command: str,
     check: bool = True,
@@ -60,26 +81,40 @@ def run_command(
 
 
 def clone_repo_mirror(
-    source: str, repo_ref: str, parent: str, mirror_loc: Path, loc: Path
+    repo_source: str, repo_ref: str, parent: str, mirror_loc: Path, loc: Path
 ) -> None:
     """
     Clone a repo source using a local git mirror.
     Assume the mirror is set up as per the Met Office
+    - repo_source: ssh url of the source repository
+    - repo_ref: git ref for the source. An empty string will get the default branch
+    - parent: Owner of the github repository being cloned (required to construct the
+              mirror path)
+    - mirror_loc: path to the local git mirrors
+    - loc: path to clone the repository to
     """
 
-    # Remove if this clone already exists
+    # If the repository exists and isn't a git repo, exit now as we don't want to
+    # overwrite it
     if loc.exists():
-        rmtree(loc)
+        if not Path(loc / ".git").exists():
+            raise RuntimeError(
+                f"The destination for the clone of {repo_source} already exists but "
+                "isn't a git directory. Exiting so as to not overwrite it."
+            )
 
-    command = f"git clone {mirror_loc} {loc}"
-    run_command(command)
+    # Clone if the repo doesn't exist
+    else:
+        command = f"git clone {mirror_loc} {loc}"
+        run_command(command)
 
-    # If not provided a ref, return
+    # If not provided a ref, pull the latest repository and return
     if not repo_ref:
+        run_command(f"git -C {loc} pull")
         return
 
-    source = source.removeprefix("git@github.com:")
-    user = source.split("/")[0]
+    repo_source = repo_source.removeprefix("git@github.com:")
+    user = repo_source.split("/")[0]
     # Check that the user is different to the Upstream User
     if user in parent.split("/")[0]:
         user = None
@@ -102,24 +137,33 @@ def clone_repo(repo_source: str, repo_ref: str, loc: Path) -> None:
     """
     Clone the repo and checkout the provided ref
     Only if a remote source
+    - repo_source: ssh url of the source repository
+    - repo_ref: git ref for the source. An empty string will get the default branch
+    - loc: path to clone the repository to
     """
 
-    # Remove if this clone already exists
-    if loc.exists():
-        rmtree(loc)
-
-    # Create a clean clone location
-    loc.mkdir(parents=True)
-
-    commands = (
-        f"git -C {loc} init",
-        f"git -C {loc} remote add origin {repo_source}",
-        f"git -C {loc} fetch origin {repo_ref}",
-        f"git -C {loc} checkout FETCH_HEAD",
-        f"git -C {loc} fetch origin main:main",
-    )
-    for command in commands:
-        run_command(command)
+    if not loc.exists():
+        # Create a clean clone location
+        loc.mkdir(parents=True)
+
+        # This process is equivalent to doing a git clone
+        # It saves a small amount of space by not fetching all refs
+        commands = (
+            f"git -C {loc} init",
+            f"git -C {loc} remote add origin {repo_source}",
+            f"git -C {loc} fetch origin {repo_ref}",
+            f"git -C {loc} checkout FETCH_HEAD",
+            f"git -C {loc} fetch origin main:main",
+        )
+        for command in commands:
+            run_command(command)
+    else:
+        commands = (
+            f"git -C {loc} fetch origin {repo_ref}",
+            f"git -C {loc} checkout FETCH_HEAD",
+        )
+        for command in commands:
+            run_command(command)
 
 
 def sync_repo(repo_source: str, repo_ref: str, loc: Path) -> None: