There are 5079 commits in trunk, which means there are 12.9 million
unordered pairs of git hashes. git uses 7 characters for short git
hashes by default, though some git tools will use longer hashes for
ambiguous commits. In fact, we already have that situation: the seven
character string "fa5eca0" is a prefix of two different commit hashes
in the "master" branch.
Consider using longer hashes in the future in your tooling and your
references to commits that appear in bug reports or comments or the
like. A bug report that referenced fa5eca0 would now be ambiguous.