feat: add features.version value

.gitattributes

@@ -1 +1,2 @@
+python/features.bzl export-subst
 tools/publish/*.txt linguist-generated=true

CHANGELOG.md

@@ -47,6 +47,7 @@ A brief description of the categories of changes:
   `requirements_linux.txt`, `requirements_windows.txt` for each respective OS
   and one extra file `requirements_universal.txt` if you prefer a single file.
   The `requirements.txt` file may be removed in the future.
+* The rules_python version is now reported in `//python/features.bzl#features.version`
 
 {#v0-0-0-removed}
 ### Removed

python/features.bzl

@@ -13,6 +13,11 @@
 # limitations under the License.
 """Allows detecting of rules_python features that aren't easily detected."""
 
+# This is a magic string expanded by `git archive`, as set by `.gitattributes`
+# See https://git-scm.com/docs/git-archive/2.29.0#Documentation/git-archive.txt-export-subst
+_VERSION_PRIVATE = "$Format:%(describe:tags=true)$"
+
 features = struct(
+    version = _VERSION_PRIVATE if "$Format" not in _VERSION_PRIVATE else "",
     precompile = True,
 )