Narrow scope of minimum version error messages

[ParkerRobb]

When trying to run git filter-repo on a repo, I kept getting an Error: need git >= 2.22.0 message, even though I have both git versions 2.37.1 and 2.41.0 installed on my system.

Initially I spent a long time trying to figure out if git-filter-repo was pointing to an old version of git (2.10.0) I had recently uninstalled, or something like that.

After tracking the error message to line 2092 of the Python script, I was able to figure out that prior lines were looking for certain things in the output of git diff-tree -h:

git-filter-repo/git-filter-repo

Lines 2085 to 2092 in 4bc9022

	# If we don't have fast-exoprt --reencode, we may also be missing
	# diff-tree --combined-all-paths, which is even more important...
	p = subproc.Popen('git diff-tree -h'.split(),
	stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
	output = p.stdout.read()
	if b'--combined-all-paths' not in output:
	# We need a version of git-diff-tree with --combined-all-paths
	raise SystemExit(_("Error: need git >= 2.22.0"))

I ran git diff-tree -h on my repo and found that I get error messages from git itself because something's wrong with my repo.

My point is that the canned error message thrown by git-filter-repo was hiding the real problem (that git itself was throwing errors when trying to operate on my repo) and opaquely telling me things that weren't true (that I had the wrong git version installed). The opaqueness of git-filter-repo's error message misdirected me and caused me to spend way longer than necessary trying to fix the problem. Narrowing the scope of and clarifying the error messages thrown by git-filter-repo would prevent people from going on a wild goose chase and spending hours trying to fix problems that do not actually exist.