Re: git merge -s subtree seems to be broken.

George Shammas [off-list ref] writes:

Bisecting around, this might be the commit that introduced the breakage.

https://github.com/git/git/commit/d8febde

Interesting.  I've never used the "-s subtree" strategy without
"-Xsubtree=..." to explicitly tell where the thing should go for a
long time, so I am not surprised if I did not notice if an update to
the heuristics made long time ago had affected tree matching.

d8febde3 ("match-trees: simplify score_trees() using tree_entry()",
2013-03-24) does touch the area that may affect the subtree matching
behaviour.

Because it is an update to heuristics, and as such, we need to be
careful when saying it is or is not "broken".  Some heuristics may
work better with your particular case, and may do worse with other
cases.

But from the log message description, it looks like it was meant to
be a no-op simplification rewrite that should not affect the outcome,
so it is a bit surprising.