feat(git): override branch.autosetupmerge=false via CLAUDE_ENV_FILE

git/.claude-plugin/plugin.json

@@ -1,6 +1,6 @@
 {
   "name": "git",
-  "version": "1.4.0",
+  "version": "1.5.0",
   "description": "Dynamic git instructions via SessionStart hook with mainline detection, conventional commits, fork handling, and safety guardrails",
   "author": {
     "name": "cblecker",

git/CLAUDE.md

@@ -8,11 +8,12 @@ are needed.
 
 ```text
 SessionStart → git-instructions.sh → stdout (instructions injected as context)
-                    ↓
+                    ↓                → CLAUDE_ENV_FILE (git config overrides)
               1. Detect mainline branch
               2. Detect conventional commits
               3. Detect fork setup
               4. Output instructions with detected values
+              5. Write git config env overrides (if CLAUDE_ENV_FILE available)
 ```
 
 ### Prerequisite
@@ -62,6 +63,25 @@ instructions and warn the user if both built-in and plugin instructions are
 present. This keeps detection logic out of the script and lets Claude handle it
 contextually.
 
+### Git config overrides via environment
+
+Rather than modifying git config files (which the safety protocol forbids), the
+script writes `GIT_CONFIG_COUNT`/`GIT_CONFIG_KEY_n`/`GIT_CONFIG_VALUE_n`
+environment variables to `CLAUDE_ENV_FILE`. These override git settings for the
+session without persisting to disk.
+
+The entries use deferred expansion via a single-quoted heredoc: literal
+`${GIT_CONFIG_COUNT:-0}` references are written to the file and expand at
+source-time. This makes the approach additive — if another plugin or the parent
+environment has already set entries, our entries append at the next available
+index rather than overwriting.
+
+Current overrides:
+
+| Setting | Value | Reason |
+|---------|-------|--------|
+| `branch.autosetupmerge` | `false` | Prevents unintended tracking setup when creating branches |
+
 ### Differences from built-in instructions
 
 - `main/master` replaced with detected mainline branch name

git/README.md

@@ -25,6 +25,7 @@ At session start, the plugin runs a detection script that:
 1. **Detects your mainline branch** (via `origin HEAD`, falls back to `main`/`master`)
 2. **Detects conventional commits** (commitlint config or commit history analysis)
 3. **Detects fork setup** (checks for `upstream` remote)
+4. **Sets git config overrides** via `CLAUDE_ENV_FILE` environment variables
 
 Then injects tailored git instructions covering:
 
@@ -53,6 +54,15 @@ The plugin auto-detects repository conventions at session start.
 | Conventional commits | commitlint config files, commit history pattern matching |
 | Fork setup | Presence of `upstream` remote |
 
+### Git Config Overrides
+
+When `CLAUDE_ENV_FILE` is available, the plugin writes environment variables to
+override git settings for the session (without modifying git config files):
+
+| Setting | Value | Reason |
+|---------|-------|--------|
+| `branch.autosetupmerge` | `false` | Prevents unintended tracking when creating branches |
+
 ## Testing
 
 Validate the plugin:

git/scripts/git-instructions.sh

@@ -274,3 +274,14 @@ ${BRANCH_NAMING}
 - Check \`git branch\` before creating to avoid duplicates
 
 EOF
+
+###############################################################################
+# Environment: Git config overrides via CLAUDE_ENV_FILE
+###############################################################################
+if [[ -n "${CLAUDE_ENV_FILE:-}" ]]; then
+  cat >> "${CLAUDE_ENV_FILE}" <<'ENVEOF'
+export GIT_CONFIG_KEY_${GIT_CONFIG_COUNT:-0}=branch.autosetupmerge
+export GIT_CONFIG_VALUE_${GIT_CONFIG_COUNT:-0}=false
+export GIT_CONFIG_COUNT=$(( ${GIT_CONFIG_COUNT:-0} + 1 ))
+ENVEOF
+fi