Feature request: config option to include binary files in scans

It would be helpful for some users to have an option to include binary files in scans -- for example, to match a domain pattern or username in a Kerberos keytab. Currently, such files are always excluded from git-secrets scans through an option passed to git grep.

The issue identifies the git grep option that currently excludes binary files, so start by locating the scan command and how configuration options are passed to git grep. Define and document the binary-file setting, then verify that scans can match the stated Kerberos keytab patterns while retaining the current default behavior; the issue names no tests or files to run.

Written by the indexing model from the issue text.