wrt your issue yes it's true that for short series of patches, it's often asked to rebase it on a clean state if it doesn't merges fully, though if you're doing a complicated work, meaning dozens of patches e.g., it's usually two things:

  • you're a regular contributor ;
  • you spend quite some time working on it.

When this happens, upstreams are usually okay with merging from a public repository that you would set-up. Though, it's usually a tiny more work for the upstreams to work with a new remote repository, and those are only used for these cases.

Also note that upstream could really fake the same work branching off from the point you branched off, and using git-am from that point instead of git am -3 on the top of the current devel branch (which is similar to a rebase, hence creates new sha's).

IOW, it's not really a git deficiency (even if git-format-patch could maybe annotate _more_ where it comes from, and git-am grok that to re-create a topic branch from that) as git has the features, just that it probably doesn't make it easy enough, and that people usually don't care enough for very short series.