diff --git a/.appveyor.yml b/.appveyor.yml
index 3745d7e..dc1edee 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -15,6 +15,6 @@ init:
 - cmd: set PATH=%PY_DIR%;%PY_DIR%\Scripts;%PATH%
 
 install: pip install -e .[tests]
-  
+
 test_script: pytest -rsv
 
diff --git a/meld_all.py b/meld_all.py
new file mode 100644
index 0000000..00ad268
--- /dev/null
+++ b/meld_all.py
@@ -0,0 +1,61 @@
+#!/usr/bin/env python
+"""
+useful for updating templates.
+
+e.g.
+
+meld_all .appveyor.yml
+
+meld_all .appveyor.yml -l Fortran
+"""
+from pathlib import Path
+from argparse import ArgumentParser
+import filecmp
+import subprocess
+try:
+    import ghlinguist as ghl
+    LANG = ghl.linguist(Path(__file__).parent, rtype=True)
+except ImportError:
+    ghl = None
+
+EXE = 'meld'
+
+
+def meldloop(root: Path, filename: Path, language: str=LANG, exe: str=EXE):
+    flist = list(root.rglob(filename.name))
+
+    print(f'comparing {len(flist)} files vs {filename}')
+
+    # Not using check_call due to spurious errors
+    for f in flist:
+        if filecmp.cmp(f, filename, shallow=False):
+            continue
+
+        if ghl is not None:
+            if ghl.linguist(f.parent, rtype=True) != language:
+                continue
+
+        subprocess.run([exe, str(filename), str(f)])
+
+
+def main():
+    p = ArgumentParser()
+    p.add_argument('filename', help='filename to compare against')
+    p.add_argument('root', help='top-level directory to search under', nargs='?')
+    p.add_argument('-l', '--language', help='language to template', default=LANG)
+    p.add_argument('-exe', help='program to compare with', default=EXE)
+    p = p.parse_args()
+
+    fn = Path(p.filename).expanduser()
+    if not fn.is_file():
+        raise FileNotFoundError(f'{fn} is not a file')
+
+    root = fn.resolve().parents[1] if not p.root else Path(p.root).expanduser()
+    if not root.is_dir():
+        raise FileNotFoundError(f'{root} is not a directory')
+
+    meldloop(root, fn, p.language, p.exe)
+
+
+if __name__ == '__main__':
+    main()
diff --git a/setup.cfg b/setup.cfg
index cedd205..6361f4f 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -43,6 +43,8 @@ tests =
   mypy
 io = 
   pycurl
+meld = 
+  ghlinguist
 
 [options.entry_points]
 console_scripts =
@@ -54,6 +56,7 @@ console_scripts =
   findvid = findvid:main
   getIP = getIP:main
   memfree = memfree:main
+  meld_all = meld_all:main
   spellcheck = spellcheck:main
   tarcp = tarcp:main