)

The current version of github.com/pkg/diff.Diff has quadratic behaviour.
This means that when we attempt a diff between relatively modest sized
files, it's easy to find yourself out of memory.

Therefore, when we see a diff between two large files (large defined in
terms of number of lines), tersely report that as if the two were binary
files, i.e. do not try to render the diff.

When github.com/pkg/diff or similar supports a linear algorithm:

golang/go#45200 (comment)

we can revert this change.

Fuzzing support brought a new parameter to MainStart,
as well as more methods on testDeps.
Use build tags to support those without breaking 1.16 nor 1.17.

While at it, bump CI to test the two latest Go versions,
and run 1.17's gofmt, as CI demands it.

Finally, make CI also test with Go's master version,
to ensure that we are compatible with it.
We pin a specific commit, since that keeps CI stable.

Fixes #144.

Co-authored-by: Roger Peppe <rogpeppe@gmail.com>

In https://go-review.googlesource.com/c/go/+/354632,
one of the struct field names in corpusEntry got renamed.

A minor change with a very easy fix.
Still, this probably signals that we shouldn't release a tagged version
with Go 1.18 support just yet, as it's still in flux.

Bump the Go tip version we test against, too.