Block remote branch deletion and improve force push error messages (#39)

- Block `git push origin --delete` and colon-refspec deletion — deleting
  remote branches closes associated PRs, which is not recoverable
- Block `--force-with-lease` — was bypassing the regex due to word
  boundary matching; all force push variants now blocked uniformly
- Force push error message now suggests `git merge` as the correct
  workaround instead of leaving the agent to improvise
- Fix README: error handling documented as "fails open" but code
  actually fails closed

Co-authored-by: AnExiledDev <AnExiledDev@users.noreply.github.com>

Author: AnExiledDev

.devcontainer/CHANGELOG.md

@@ -2,6 +2,14 @@
 
 ## [Unreleased]
 
+### Fixed
+
+#### Dangerous Command Blocker
+- **Force push block now suggests `git merge` as workaround** — error message explains how to avoid diverged history instead of leaving the agent to improvise destructive workarounds
+- **Block `--force-with-lease`** — was slipping through regex; all force push variants now blocked uniformly
+- **Block remote branch deletion** — `git push origin --delete` and colon-refspec deletion (`git push origin :branch`) now blocked; deleting remote branches closes associated PRs
+- **Fixed README** — error handling was documented as "fails open" but code actually fails closed; corrected to match behavior
+
 ### Added
 
 #### Documentation

.devcontainer/plugins/devs-marketplace/plugins/dangerous-command-blocker/README.md

@@ -14,7 +14,8 @@ Inspects every Bash command Claude attempts to run against a set of dangerous pa
 | Privileged deletion | `sudo rm` |
 | World-writable permissions | `chmod 777`, `chmod -R 777` |
 | Force push to main/master | `git push --force origin main`, `git push -f origin master` |
-| Bare force push | `git push -f`, `git push --force` (no branch specified) |
+| Bare force push | `git push -f`, `git push --force`, `git push --force-with-lease` |
+| Remote branch deletion | `git push origin --delete`, `git push origin :branch` |
 | Git history destruction | `git reset --hard origin/main`, `git clean -f` |
 | System directory writes | `> /usr/`, `> /etc/`, `> /bin/`, `> /sbin/` |
 | Disk formatting | `mkfs.*`, `dd of=/dev/` |
@@ -47,7 +48,7 @@ Claude calls the Bash tool
 ### Error Handling
 
 - **JSON parse failure**: Fails closed (exit 2) — if the input can't be read, the command is blocked
-- **Other exceptions**: Fails open (exit 0) — logs the error to stderr but does not block
+- **Other exceptions**: Fails closed (exit 2) — logs the error to stderr and blocks
 
 ### Timeout
 

.devcontainer/plugins/devs-marketplace/plugins/dangerous-command-blocker/scripts/block-dangerous.py

@@ -11,6 +11,13 @@
 import re
 import sys
 
+FORCE_PUSH_SUGGESTION = (
+    "Blocked: force push is not allowed. "
+    "If you rebased and need to update a remote branch, use "
+    "`git merge origin/main` instead of `git rebase` to avoid "
+    "diverged history that requires force push."
+)
+
 DANGEROUS_PATTERNS = [
     # Destructive filesystem deletion
     (
@@ -79,16 +86,30 @@
     (r"\brm\s+.*-[^\s]*r[^\s]*f[^\s]*\s+\.\./", "Blocked: rm -rf on parent directory"),
     (r"\bfind\s+.*-exec\s+rm\b", "Blocked: find -exec rm is dangerous"),
     (r"\bfind\s+.*-delete\b", "Blocked: find -delete is dangerous"),
-    # Git history destruction
-    (r"\bgit\s+push\s+-f\b", "Blocked: bare force push - specify remote and branch"),
-    (
-        r"\bgit\s+push\s+--force\b",
-        "Blocked: bare force push - specify remote and branch",
-    ),
+    # Git history destruction — force push (all variants)
+    (r"\bgit\s+push\s+-f\b", FORCE_PUSH_SUGGESTION),
+    (r"\bgit\s+push\s+--force\b", FORCE_PUSH_SUGGESTION),
+    (r"\bgit\s+push\s+--force-with-lease\b", FORCE_PUSH_SUGGESTION),
     (
         r"\bgit\s+clean\s+-[^\s]*f",
         "Blocked: git clean -f removes untracked files permanently",
     ),
+    # Remote branch deletion — closes open PRs and destroys remote history
+    (
+        r"\bgit\s+push\s+\S+\s+--delete\b",
+        "Blocked: deleting remote branches closes any associated pull requests. "
+        "Do not delete remote branches as a workaround for force push blocks.",
+    ),
+    (
+        r"\bgit\s+push\s+--delete\b",
+        "Blocked: deleting remote branches closes any associated pull requests. "
+        "Do not delete remote branches as a workaround for force push blocks.",
+    ),
+    (
+        r"\bgit\s+push\s+\S+\s+:\S",
+        "Blocked: push with colon-refspec deletes remote branches and closes "
+        "associated pull requests. Do not use as a workaround for force push blocks.",
+    ),
 ]