build: add comment with rules for libtool version update

diff --git a/Makefile.am b/Makefile.am
index c2fac723f070d0863a3304ae97eeb592b2008869..99a69f682f9d925ae0b1154bbc5c25c1ebf3f71a 100644 (file)
--- a/Makefile.am
+++ b/Makefile.am
@@ -44,6 +44,19 @@ SED_PROCESS = \
 %.pc: %.pc.in Makefile
        $(SED_PROCESS)
 
+# Rules for libtool versioning (from https://www.gnu.org/software/libtool/manual/html_node/Updating-version-info.html)
+# 1. Start with version information of ‘0:0:0’ for each libtool library.
+# 2. Update the version information only immediately before a public release of
+#    your software. More frequent updates are unnecessary, and only guarantee that
+#    the current interface number gets larger faster.
+# 3. If the library source code has changed at all since the last update, then
+#    increment revision (‘c:r:a’ becomes ‘c:r+1:a’).
+# 4. If any interfaces have been added, removed, or changed since the last
+#    update, increment current, and set revision to 0.
+# 5. If any interfaces have been added since the last public release, then
+#    increment age.
+# 6. If any interfaces have been removed or changed since the last public
+#    release, then set age to 0.
 LIBKMOD_CURRENT=5
 LIBKMOD_REVISION=5
 LIBKMOD_AGE=3