Display git commit info in the /about section. (#567)

This change detects the most recent git commit short hash and writes it to the `GIT_COMMIT_INFO` constant in `packages/cli/src/generated/git-commit.sh`, optionally appending the string "(local modifications)" if additional local changes after that commit are detected.

If set, this string is displayed in the `/about` dialog as well as passed into the `/bug` template.

Example:

```
> /about

╭───────────────────────────────────────────────────────────────────────────╮
│                                                                           │
│ About Gemini CLI                                                          │
│                                                                           │
│ CLI Version               development                                     │
│ Git Commit                43370ab (local modifications)                   │
│ Model                     gemini-2.5-pro-preview-05-06                    │
│ Sandbox                   sandbox-exec (minimal)                          │
│ OS                        darwin v23.11.0                                 │
│                                                                           │
╰───────────────────────────────────────────────────────────────────────────╯
```

Additionally, this change updates `.gitignore` to ignore the generated files, `scripts/clean.sh` to remove them, and adds a `npm run generate` stage for this and any other generators we need to write.

1 files changed, 44 insertions, 0 deletions

diff --git a/scripts/generate-git-commit-info.sh b/scripts/generate-git-commit-info.sh
new file mode 100755
index 00000000..2a64830f
--- /dev/null
+++ b/scripts/generate-git-commit-info.sh
@@ -0,0 +1,44 @@
+#!/bin/bash
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+set -euo pipefail
+
+GENERATED_DIR="packages/cli/src/generated"
+GIT_COMMIT_FILE="$GENERATED_DIR/git-commit.ts"
+GIT_COMMIT_INFO="N/A"
+
+mkdir -p "$GENERATED_DIR"
+
+if command -v git &> /dev/null && git rev-parse --is-inside-work-tree &> /dev/null; then
+    GIT_HASH=$(git rev-parse --short HEAD 2>/dev/null || echo "")
+    if [ -n "$GIT_HASH" ]; then
+        GIT_COMMIT_INFO="$GIT_HASH"
+        if [ -n "$(git status --porcelain 2>/dev/null)" ]; then
+            GIT_COMMIT_INFO="$GIT_HASH (local modifications)"
+        fi
+    fi
+fi
+
+cat <<EOL > "$GIT_COMMIT_FILE"
+/**
+ * @license
+ * Copyright $(date +%Y) Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+// This file is auto-generated by the build script (scripts/build.sh)
+// Do not edit this file manually.
+export const GIT_COMMIT_INFO = '$GIT_COMMIT_INFO';
+EOL