Re: On blame/pickaxe

Petr Baudis [off-list ref] writes:

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If the user is not prepared to see code movement, pickaxe can be
run without -M nor -C to get the classic blame output.

Ok, so in this case -M and -C does not mean just looking for
copies/movements in other files but inside the same file as well.

Perhaps we might want to differentiate those two cases since searching
in all files might be significantly slower.

I do not personally worry about people confusing -M/-C to
pickaxe with -M/-C given to diff (to pickaxe, use of diff is
purely an internal implementation issue), and reused -M and -C
to mean quite different things.  -M is to detect line movement
inside a file (it is not strictly limited to "line movement",
though. It _is_ about "copies and moves within the same file").
On the other hand, -C (and its stronger form -C -C) is to detect
copies and moves across file boundaries (but wholesale "file
rename" comes as part of the basic algorithm so you do not have
to ask for it with -M nor -C).  So in that sense pronouncing M
"move" and C "copy" is not accurate.  Their differences is
already what you said "we might want".

However they match the cost expectation people are used to in
diff options pretty well.  -M is not so expensive and -C is
somewhat.  -C -C is like find-copies-harder and is quite
expensive.

Also currently the code does not do "move" detection at all.
Contrary to intuition, move detection is more expensive than
copy detection in this case.