Git includes a grep command to search through commits to a repo as well as the local files in the repo directory: git grep. Sometimes it is useful to search for a string throughout an entire repo, e.g. to find where an error message is produced.
By itself, git grep searches the currently checked out branch and local files for a regular expression. Sometimes the text we want to find is on another branch, which may actually be deployed and running in some environment. Therefore, it is useful to search through all branches of a repository to be certain where some string of interest is generated, a file is written, etc.
To search through all branches of a git repo for a string, use:
$ git grep str $(git rev-list --all)
To search through all branches ignoring string case:
$ git grep -i str $(git rev-list --all)
This can also be done with regular expressions:
$ git grep -i RegEx $(git rev-list --all)