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+;;; git_status.el --- Read-only git status tool for gptel -*- coding: utf-8; lexical-binding: t; -*-
+
+;; Author: Craig Jennings <c@cjennings.net>
+;; Keywords: convenience, tools, git
+
+;; This file is not part of GNU Emacs.
+
+;;; Commentary:
+
+;; Gptel tool returning `git status --short --branch' for a path under
+;; the user's home directory.  Read-only: never writes to the repo,
+;; never runs anything that could mutate state.  Path validation
+;; rejects anything outside HOME and any path that doesn't resolve to
+;; a directory inside a git working tree.
+
+;;; Code:
+
+(require 'gptel)
+(require 'cl-lib)
+
+(defun cj/gptel-git-status--validate-path (path)
+  "Validate PATH as a usable working directory for a git status call.
+PATH must resolve under the user's home directory, must be an
+existing directory, and must be inside a git working tree.  Returns
+the expanded path string on success; signals `error' otherwise."
+  (let ((full (expand-file-name (or path "~") "~")))
+    (unless (string-prefix-p (expand-file-name "~") full)
+      (error "Path must be within home directory: %s" path))
+    (unless (file-directory-p full)
+      (error "Not a directory: %s" full))
+    (let ((default-directory full))
+      (unless (zerop (process-file "git" nil nil nil
+                                   "rev-parse" "--is-inside-work-tree"))
+        (error "Not a git working tree: %s" full)))
+    full))
+
+(defun cj/gptel-git-status--run (path)
+  "Run `git status --short --branch' in PATH.  Return the output.
+Color is disabled via `-c color.ui=false' at the git level (`git status'
+itself doesn't accept `--no-color' like `git log' / `git diff' do)."
+  (let* ((dir (cj/gptel-git-status--validate-path path))
+         (default-directory dir))
+    (with-temp-buffer
+      (let ((exit (process-file "git" nil t nil
+                                "-c" "color.ui=false"
+                                "status" "--short" "--branch")))
+        (unless (zerop exit)
+          (error "git status exited with %d: %s" exit (buffer-string)))
+        ;; `--branch' always prints a `## <branch>' header, so empty
+        ;; output is unreachable.  Detect a clean tree by counting the
+        ;; non-branch lines: if only the header is present, no files
+        ;; are modified / staged / untracked.
+        (let* ((out (buffer-string))
+               (non-branch-lines
+                (cl-count-if
+                 (lambda (l)
+                   (and (not (string-empty-p l))
+                        (not (string-prefix-p "## " l))))
+                 (split-string out "\n"))))
+          (if (zerop non-branch-lines)
+              (format "Clean working tree in %s\n%s" dir (string-trim out))
+            out))))))
+
+(with-eval-after-load 'gptel
+  (gptel-make-tool
+   :name "git_status"
+   :function (lambda (path) (cj/gptel-git-status--run path))
+   :description "Return the output of `git status --short --branch' for a directory in the user's home tree.  Read-only.  Useful for seeing which files are modified, staged, or untracked, and how the current branch compares to its upstream."
+   :args (list '(:name "path"
+                       :type string
+                       :description "Directory inside a git working tree.  Either an absolute path under the user's home directory or a path relative to it (e.g. 'code/myproject')."))
+   :category "git"
+   :confirm nil
+   :include t)
+
+  (add-to-list 'gptel-tools (gptel-get-tool '("git" "git_status"))))
+
+(provide 'git_status)
+;;; git_status.el ends here