snap: Incorporate selective-checkout to ensure a revision for stable channel is always available

Refer-to: Selective-checkout: Check out the tagged release revision if it isn't promoted to the stable channel - doc - snapcraft.io <https://forum.snapcraft.io/t/selective-checkout-check-out-the-tagged-release-revision-if-it-isnt-promoted-to-the-stable-channel/10617>
Refer-to: Releasing your app - Documentation for snaps: Universal Linux packages <https://docs.snapcraft.io/releasing-your-app/6795>
Signed-off-by: 林博仁(Buo-ren Lin) <Buo.Ren.Lin@gmail.com>

snap/snapcraft.yaml

@@ -43,6 +43,8 @@ plugs:
 
 parts:
   glances:
+    after:
+    - selective-checkout
     plugin: python
     source: .
     # FIXME: Theoretically this also replaces `summary` and `description`
@@ -52,8 +54,7 @@ parts:
     parse-info: [setup.py]
     override-pull: |
       snapcraftctl pull
-      snapcraftctl set-version \
+      "$SNAPCRAFT_STAGE"/scriptlets/selective-checkout
-        "$(git describe --always --dirty --tags --match 'v*' | sed s/^v//)"
   bottle:
     plugin: python
     source: https://github.com/bottlepy/bottle.git
@@ -69,3 +70,11 @@ parts:
     plugin: dump
     organize:
       '*': bin/
+  selective-checkout:
+    plugin: nil
+    build-packages:
+    - git
+    stage-snaps:
+    - selective-checkout
+    prime:
+    - -*