Add build info to post-build.sh

board/raspberrypi/post-build.sh

@@ -34,4 +34,36 @@ auto wlan0
 iface wlan0 inet dhcp
     pre-up ip link set wlan0 up
     pre-up wpa_supplicant -B -i wlan0 -c /etc/wpa_supplicant.conf
+EOF
+
+# Generate /etc/build-info with details about this build
+build_user="$(id -un)"
+build_host="$(hostname)"
+build_date="$(date '+%Y-%m-%d %H:%M:%S %z')"
+
+# Determine the git revision the same way the Linux kernel does:
+# prefer a tag (git describe), fall back to the short hash, and append
+# "-dirty" if tracked files are modified or there are untracked files.
+build_rev="unknown"
+if [ -n "$BR2_EXTERNAL_RPI_COMMON_PATH" ] && \
+   git -C "$BR2_EXTERNAL_RPI_COMMON_PATH" rev-parse --is-inside-work-tree >/dev/null 2>&1; then
+    git_dir="$BR2_EXTERNAL_RPI_COMMON_PATH"
+    build_rev="$(git -C "$git_dir" describe --always --tags 2>/dev/null || \
+                 git -C "$git_dir" rev-parse --short HEAD 2>/dev/null || \
+                 echo unknown)"
+    # Refresh the index so diff-index doesn't report stale stat info
+    git -C "$git_dir" update-index --refresh >/dev/null 2>&1 || :
+    dirty=""
+    if ! git -C "$git_dir" diff-index --quiet HEAD -- 2>/dev/null; then
+        dirty="-dirty"
+    elif [ -n "$(git -C "$git_dir" ls-files --others --exclude-standard 2>/dev/null)" ]; then
+        dirty="-dirty"
+    fi
+    build_rev="${build_rev}${dirty}"
+fi
+
+cat > "$TARGET_DIR/etc/build-info" << EOF
+Built by: ${build_user}@${build_host}
+Build date: ${build_date}
+Revision: ${build_rev}
 EOF