feat(bazel): introduce a binary stamping feature (#22176)

This grabs version control metadata and makes it available in the build, eg. to put in the version field for released artifacts

PR Close #22176

tools/BUILD.bazel

@@ -1 +1,9 @@
-# Marker file indicating this folder is a Bazel package
+# Executes the workspace_status_command and provides the result.
+# See the section on stamping in docs/BAZEL.md
+genrule(
+    name = "stamp_data",
+    outs = ["stamp_data.txt"],
+    cmd = "cat bazel-out/volatile-status.txt > $@",
+    stamp = True,
+    visibility = ["//:__subpackages__"],
+)

tools/bazel.rc

@@ -21,6 +21,12 @@ build --symlink_prefix=dist/
 # Performance: avoid stat'ing input files
 build --watchfs
 
+###############################
+# Release support             #
+###############################
+
+build --workspace_status_command=./tools/bazel_stamp_vars.sh
+
 ###############################
 # Output                      #
 ###############################

tools/bazel_stamp_vars.sh

@@ -0,0 +1,42 @@
+#!/usr/bin/env bash
+# Generates the data used by the stamping feature in bazel.
+# A genrule with stamp=1 can read the resulting file from bazel-out/volatile-status.txt
+# See the section on stamping in docs/BAZEL.md
+
+set -u -e -E -o pipefail
+
+echo "Running: $0" >&2
+
+function onError {
+  echo "Failed to execute: $0"
+  echo ""
+}
+
+# Setup crash trap
+trap 'onError' ERR
+
+
+echo BUILD_SCM_HASH $(git rev-parse HEAD)
+
+if [[ "$(git tag)" == "" ]]; then
+  echo "No git tags found, can't stamp the build."
+  echo "Either fetch the tags:"
+  echo "       git fetch git@github.com:angular/angular.git --tags"
+  echo "or build without stamping by giving an empty workspace_status_command:"
+  echo "       bazel build --workspace_status_command= ..."
+  echo ""
+fi
+
+BUILD_SCM_VERSION_RAW=$(git describe --abbrev=7 --tags HEAD)
+
+# Find out if there are any uncommitted local changes
+# TODO(i): is it ok to use "--untracked-files=no" to ignore untracked files since they should not affect anything?
+if [[ $(git status --untracked-files=no --porcelain) ]]; then LOCAL_CHANGES="true"; else LOCAL_CHANGES="false"; fi
+echo BUILD_SCM_LOCAL_CHANGES ${LOCAL_CHANGES}
+
+# Reformat `git describe` version string into a more semver-ish string
+#   From:   5.2.0-rc.0-57-g757f886
+#   To:     5.2.0-rc.0+57.sha-757f886
+#   Or:     5.2.0-rc.0+57.sha-757f886.with-local-changes
+BUILD_SCM_VERSION="$(echo ${BUILD_SCM_VERSION_RAW} | sed -E 's/-([0-9]+)-g/+\1.sha-/g')""$( if [[ $LOCAL_CHANGES == "true" ]]; then echo ".with-local-changes"; fi)"
+echo BUILD_SCM_VERSION ${BUILD_SCM_VERSION}