git-mv: search more precisely for source directory in index
A move of a directory should find the entries in the index by searching for the name _including_ the slash. Otherwise, the directory can be shadowed by a file when it matches the prefix and is lexicographically smaller, e.g. "ab.c" shadows "ab/".
Noticed by Sergey Vlasov.
[jc: added Sergey's original reproduction recipe as a test case at the end of t7001.]
Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de> Signed-off-by: Junio C Hamano <email@example.com>