Fix CommitCommand.setOnly()

Fix CommitCommand.setOnly()

When CommitCommand.setOnly(path) is used a temporary index has to be
created containing only modifications for the specified pathes. The
process to fill this temporary index was broken because filling the
index was stopped when we reached the first untracked file. Instead the
process to fill the temporary index should continue until we processed
all pathes.

Bug: 451465
Change-Id: I22af50d70bd3b81e7c056358724956122b0d158d
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>