write guard rejects heredoc and in-place shell edits, costing a round

CHANGELOG.md

@@ -1,5 +1,8 @@
 # Changelog
 
+## 37
+- Bash write guard: the refusal says up front to Read the file before Edit (an unread Edit cost one more round), and shell writes to git-ignored files (build output, artifacts) pass like `/tmp`.
+
 ## 36
 - `gc --remove` removes copies with a submodule (git refused without `--force`) and copies whose status shows changes but content equals HEAD (a hook restored the files); a change, a stash or a commit on no remote inside a submodule still blocks removal, and so does a failed submodule check.
 

hooks/bash_guard.py

@@ -1,9 +1,10 @@
 #!/usr/bin/env python3
 """PreToolUse hook (Bash): refuse editing project files through the shell (sed -i, perl -i, cat > file <<, python3 -
-heredocs that write); Edit/Write pay only the change. Exit 2 = blocked. Temporary files pass; echo/tee > file are
-not covered on purpose."""
+heredocs that write); Edit/Write pay only the change. Exit 2 = blocked. Temporary and git-ignored files (build
+output) pass; echo/tee > file are not covered on purpose."""
 import json
 import re
+import subprocess
 import sys
 
 TEMP = ("/tmp/", "$TMPDIR", "${TMPDIR", "/dev/")
@@ -16,6 +17,12 @@
 PY_WRITES = re.compile(r"\.write_(?:text|bytes)\(|\bopen\([^)]*['\"][wax]b?\+?['\"]")
 
 
+def scratch(path):
+    """Not a project file: temporary or ignored by git (build output, artifacts)."""
+    return path.startswith(TEMP) or subprocess.run(["git", "check-ignore", "-q", "--", path],
+                                                   capture_output=True).returncode == 0
+
+
 def split(cmd):
     """(command lines with quoted strings removed, heredoc bodies)."""
     lines, bodies, end = [], [], None
@@ -41,7 +48,7 @@ def edits(ln):
             continue
         seg = re.split(r"[|;&]", ln[m.end():], maxsplit=1)[0]  # this command only, not `; rm /tmp/x` after it
         target = m.group(1) if m.groups() else (seg.split() or [""])[-1]
-        if not target.startswith(TEMP):  # temporary files are not project files
+        if not scratch(target):
             return what
     return None
 
@@ -53,14 +60,15 @@ def main():
         return 0
     lines, body = split(cmd)
     hits = [w for w in map(edits, lines) if w]
-    writes = [ln for ln in body.split("\n") if PY_WRITES.search(ln) and not any(t.strip("/") in ln for t in TEMP)]
+    writes = [ln for ln in body.split("\n") if PY_WRITES.search(ln) and not any(t.strip("/") in ln for t in TEMP)
+              and not any(scratch(p) for p in re.findall(r"['\"]([^'\"\s]*/[^'\"\s]*)['\"]", ln))]
     if any(PY_HEREDOC.search(ln) for ln in lines) and writes:
         hits.append("python3 - writing files")
     if not hits:
         return 0
-    print(f"dpcli: {hits[0]} edits project files through the shell — use the Edit tool (exact replacement) or Write "
-          f"(new file); read with Read; bulk renames: ast-grep run -p OLD -r NEW -U. Temporary files (/tmp) are fine.",
-          file=sys.stderr)
+    print(f"dpcli: {hits[0]} edits project files through the shell. Read the file first (cat in Bash does not count), "
+          f"then Edit (exact replacement); a new file — Write; bulk renames: ast-grep run -p OLD -r NEW -U. "
+          f"Temporary (/tmp) and git-ignored files (build/) are fine.", file=sys.stderr)
     return 2
 
 

lib/dpcli/__init__.py

@@ -6,4 +6,4 @@
 else in the current copy. Exit codes: 0 ok, 1 error/check failed, 2 arguments.
 """
 
-VERSION = 36  # bump on every change: older copies re-exec from the main copy (reexec.maybe_reexec)
+VERSION = 37  # bump on every change: older copies re-exec from the main copy (reexec.maybe_reexec)

tests/test_bash_guard.py

@@ -9,9 +9,9 @@
 GUARD = DIST / "hooks" / "bash_guard.py"
 
 
-def run(cmd):
+def run(cmd, cwd=None):
     r = subprocess.run([sys.executable, str(GUARD)], input=json.dumps({"tool_name": "Bash", "tool_input": {"command": cmd}}),
-                       capture_output=True, text=True)
+                       capture_output=True, text=True, cwd=cwd)
     return r.returncode, r.stderr
 
 
@@ -30,6 +30,16 @@ def test_blocks_shell_edits(self):
             code, err = run(cmd)
             self.assertEqual(code, 2, cmd)
             self.assertIn("Edit", err)
+        self.assertIn("Read the file first", err)  # Edit refuses an unread file: say so now, not one round later
+
+    def test_allows_git_ignored_targets(self):
+        p = Project()
+        self.addCleanup(p.cleanup)
+        (p.root / ".gitignore").write_text("build/\n")
+        for cmd in ("cat > build/r.json <<'EOF'\n{}\nEOF", "sed -i s/a/b/ build/x.md",
+                    "python3 - <<'EOF'\nopen('build/a.txt', 'w').write('x')\nEOF"):
+            self.assertEqual(run(cmd, p.root)[0], 0, cmd)
+        self.assertEqual(run("sed -i s/a/b/ src/x.ts", p.root)[0], 2)
 
     def test_allows_programs_reads_and_quoted_text(self):
         for cmd in ("rg -n foo src", "sed -n '1,20p' f", "python3 - <<'EOF'\nprint(1)\nEOF", "cat f | jq .",