Add rationale for a couple font version checks

com.google.fonts/check/family/equal_font_versions
com.google.fonts/check/font_version
On the Open Type Profile.

(PR #4570)

CHANGELOG.md

@@ -32,6 +32,8 @@ A more detailed list of changes is available in the corresponding milestones for
   - **[com.adobe.fonts/check/fsselection_matches_macstyle]:** Improve log messages to include the bit values. (PR #4570)
   - **[com.google.fonts/check/fsselection]:** Added rationale. (PR #4570)
   - **[com.google.fonts/check/family/equal_unicode_encodings]:** Added rationale, even though this is a questionable check, which we may simply deprecate, as we're not sure why would we expect what it checks. (PR #4570)
+  - **[com.google.fonts/check/family/equal_font_versions]:** Added rationale. (PR #4570)
+  - **[com.google.fonts/check/font_version]:** Added rationale. (PR #4570)
 
 
 ## 0.12.0a2 (2024-Feb-21)

Lib/fontbakery/checks/opentype/head.py

@@ -7,7 +7,12 @@
 
 
 @check(
-    id="com.google.fonts/check/family/equal_font_versions", proposal="legacy:check/014"
+    id="com.google.fonts/check/family/equal_font_versions",
+    proposal="legacy:check/014",
+    rationale="""
+        Within a family released at the same time, all members of the family
+        should have the same version number in the head table.
+    """,
 )
 def com_google_fonts_check_family_equal_font_versions(ttFonts):
     """Make sure all font files have the same version value."""
@@ -109,7 +114,17 @@ def parse_version_string(name: str) -> float:
     return fractions.Fraction(version_string.group(1))
 
 
-@check(id="com.google.fonts/check/font_version", proposal="legacy:check/044")
+@check(
+    id="com.google.fonts/check/font_version",
+    proposal="legacy:check/044",
+    rationale="""
+            The OpenType specification provides for two fields which contain
+            the version number of the font: fontRevision in the head table,
+            and nameID 5 in the name table. If these fields do not match,
+            different applications will report different version numbers for
+            the font.
+        """,
+)
 def com_google_fonts_check_font_version(ttFont):
     """Checking font version fields (head and name table)."""