git tag issue of stem tree

This might be rather an issue related to the work flow than a real bug but I think it is worth to be reported. At a stable Gentoo system I'm not able to apply the output of

git diff 1.4.1.. | (cd /var/tmp/portage/net-libs/stem-1.4.1/work/stem-1.4.1/; patch -p1 --dry-run)

onto an unpacked 1.4.1 Gentoo package. I get a problem here :

checking file stem/descriptor/microdescriptor.py
checking file stem/descriptor/networkstatus.py
Reversed (or previously applied) patch detected!  Assume -R? [n] n
Apply anyway? [n] n
Skipping patch.
12 out of 12 hunks ignored
checking file stem/descriptor/reader.py
checking file stem/descriptor/remote.py

However this works:

git diff 1.4.0.. | (cd /var/tmp/portage/net-libs/stem-1.4.0/work/stem-1.4.0/; patch -p1 --dry-run)

Which let me wonder, if I made a mistake here -or- the git tag 1.4.1 wasn't made at a merge point of the git tree ?