lint 'lint' and make it only run on changed files

It was getting annoying how long it would take to run.

1 files changed, 25 insertions, 15 deletions

diff --git a/lint b/lint
index a69b424..9bdcc57 100755
--- a/lint
+++ b/lint
@@ -1,45 +1,55 @@
 #!/usr/bin/env python
+"""
+all your lint are belong to us
+"""
 import os
-import glob
 import subprocess
 import sys
 
 
-def run(cmd, f):
-    global ERRORS
+def run(cmd, file):
+    "Exec a linter for a file."
+    global ERRORS  # pylint: disable=global-statement
     args = {
         "ormolu": ["--mode", "check"],
         "hlint": [],
         "black": ["--quiet", "--check"],
         "pylint": [],
     }
-    ret = subprocess.run([cmd, *args[cmd], f], stdout=subprocess.PIPE)
+    # pylint: disable=subprocess-run-check
+    ret = subprocess.run([cmd, *args[cmd], file], stdout=subprocess.PIPE)
     if ret.returncode != 0:
-        ERRORS += 1
+        ERRORS += 1  # pylint: disable=undefined-variable
         msg = ret.stdout.decode("utf-8").strip()
-        print(f"lint error: {cmd} on {f}")
+        print(f"lint error: {cmd} on {file}")
         if msg:
             print(msg)
 
 
 def find_files(bizroot, extensions):
+    "Return a dict of {ext: [files]} that we should lint."
     ret = {k: [] for k in extensions}
-    for root, dirs, files in os.walk(bizroot, topdown=True):
-        (dirs.remove(d) for d in dirs if d.startswith(("_", ".")))
-        for ext in extensions:
-            for f in files:
-                if f.endswith(ext):
-                    ret[ext].append(os.path.join(root, f))
+    changed = (
+        subprocess.check_output(["git", "diff", "--cached", "--name-only"])
+        .decode("utf-8")
+        .strip()
+    )
+    for ext in extensions:
+        for file in changed:
+            if file.endswith(ext):
+                ret[ext].append(os.path.join(bizroot, file))
     return ret
 
 
 if __name__ == "__main__":
     ERRORS = 0
-    files = find_files(os.getenv("BIZ_ROOT"), [".hs", ".py"])
-    for hs in files[".hs"]:
+    FILES = find_files(os.getenv("BIZ_ROOT"), [".hs", ".py"])
+    for hs in FILES[".hs"]:
         run("ormolu", hs)
         run("hlint", hs)
-    for py in files[".py"]:
+    for py in FILES[".py"]:
         run("black", py)
         run("pylint", py)
+    run("black", __file__)
+    run("pylint", __file__)
     sys.exit(ERRORS)