name-rev: use strbuf_strip_suffix() in get_rev_name()

name-rev: use strbuf_strip_suffix() in get_rev_name()

get_name_rev() basically open-codes strip_suffix() before adding a
string to a strbuf.

Let's use the strbuf right from the beginning, i.e. add the whole
string to the strbuf and then use strbuf_strip_suffix(), making the
code more idiomatic.

Signed-off-by: René Scharfe <redacted>
Signed-off-by: SZEDER Gábor <redacted>
Signed-off-by: Junio C Hamano <redacted>