Update versioning.md (#12805)

docs/development/versioning.md

@@ -6,8 +6,9 @@
   Refers to a two digit value, eg: "2.6".
 
 **Build Version**: 
-  Refers to the product version plus the current GIT SHA. A 'build version'
-  uniquely identifies a software version, eg: `2.6+ABC123`
+  Refers to the product version plus the current commit count. Because
+  we enforce squash-commits & have a linear history, a 'build version'
+  uniquely identifies a software version, eg: `2.6.12300`
 
 ## Product Version Semantics
 
@@ -29,21 +30,22 @@ EG:
 ### Example Scenarios for Product Version Increments
 
 For example, let's say 3.0 is current. If the team releases a new version, it would be '3.1'
-If the next release version is not compatible, it would be '4.0'
-
+If the next release version is not compatible, it would be '4.0'  (TODO: what exactlky
+does "not compatible" mean? For now that means at least save-game compatibility, where
+for example 3.0 save games could not be read, then the next version would be a 4.0)
 
 
 ## Build Version Semantics
 
-```[product version]+[Git SHA]```
+```[product version].[Commit Number]```
 
 - **product version** - See above
-- **Git SHA** - The latest Git SHA (commit version)
+- **Commit Number** - How many commits there are on master. Never goes down.
 
 Eg:
 ```
-2.5+abc214aa293fb
-2.6+8805b3aa293fb
+2.5.1000
+2.6.2000
 ```
 
 ## Discussions and background