Fossil

| Option | Meaning
|--------|-------------------------------------------------------------
| `-i`   | ignore case in matches
| `-l`   | list a checkin ID prefix for matching historical versions of the file
| `-v`   | print each checkin ID considered, regardless of whether it matches

That leaves many divergences at the option level from POSIX `grep`:

*   There is no built-in way to get a count of matches, as with `grep
    -c`.

*    You cannot give more than one pattern, as with `grep -e` or `grep
     -f`.

*   There is no equivalent of `grep -F` to do literal fixed-string
    matches only.

*   `fossil grep -l` does not do precisely the same thing as POSIX
    `grep -l`: it lists checkin ID prefixes, not file names.

*   Fossil always gives the line number in its output, which is to say
    that it acts like `grep -n`.  There is no way to disable the line
    number in `fossil grep` output.

*   There is no way to suppress all output, returning only a status code
    to indicate whether the pattern matched, as with `grep -q`.

*   There is no way to suppress error output, as with `grep -s`.

*   Fossil `grep` accepts only a single input file name. You cannot give
    it a list of file names, and you cannot give it a directory name for
    Fossil to expand to the set of all files under that directory. This
    means Fossil `grep` has no equivalent of the common POSIX `grep -R`
    extension. (And if it did, it would probably have a different option
    letter, since `-R` in Fossil has a different meaning, by
    convention.)

*   You cannot invert the match, as with `grep -v`.

Patches to remove those limitations will be thoughtfully considered.


## Regular Expression Dialect

Fossil contains a built-in regular expression engine implementing a