manual: github: merge tag/commit ID examples

And reword as suggested by Samuel.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

docs/manual/adding-packages-tips.txt

@@ -43,23 +43,15 @@ Packages on github often don't have a download area with release tarballs.
 However, it is possible to download tarballs directly from the repository
 on github.
 
-If the package version matches a tag, then this tag should be used to
-identify the version:
-
-------------------------
-FOO_VERSION = v1.0
-FOO_SITE = http://github.com/<user>/<package>/tarball/$(FOO_VERSION)
-------------------------
-
-If the package has no release version, or its version cannot be
-identified using tag, then the SHA1 of the particular commit should be
-used to identify the version (the first 7 characters of the SHA1 are
-enough):
-
 ------------------------
-FOO_VERSION = 1234567
+FOO_VERSION = v1.0 # tag or (abbreviated) commit ID
 FOO_SITE = http://github.com/<user>/<package>/tarball/$(FOO_VERSION)
 ------------------------
 
-Note that the name of the tarball is the default +foo-1234567.tar.gz+
-so it is not necessary to specify it in the +.mk+ file.
+.Notes
+- The FOO_VERSION can either be a tag or a commit ID.
+- The tarball name generated by github matches the default one from
+  Buildroot (e.g.: +foo-1234567.tar.gz+),
+  so it is not necessary to specify it in the +.mk+ file.
+- When using a commit ID as version, usually the first 7 characters of
+  the SHA1 are enough.