hg grep [OPTION]... PATTERN [FILE]...

search for a pattern in specified files and revisions

    Search revisions of files for a regular expression.

    This command behaves differently than Unix grep. It only accepts
    Python/Perl regexps. It searches repository history, not the working
    directory. It always prints the revision number in which a match appears.

    By default, grep only prints output for the first revision of a file in
    which it finds a match. To get it to print every revision that contains a
    change in match status ("-" for a match that becomes a non-match, or "+"
    for a non-match that becomes a match), use the --all flag.

    Returns 0 if a match is found, 1 otherwise.

options:

 -0 --print0              end fields with NUL
    --all                 print all revisions that match
 -a --text                treat all files as text
 -f --follow              follow changeset history, or file history across
                          copies and renames
 -i --ignore-case         ignore case when matching
 -l --files-with-matches  print only filenames and revisions that match
 -n --line-number         print matching line numbers
 -r --rev REV [+]         only search files changed within revision range
 -u --user                list the author (long with -v)
 -d --date                list the date (short with -q)
 -I --include PATTERN [+] include names matching the given patterns
 -X --exclude PATTERN [+] exclude names matching the given patterns

[+] marked option can be specified multiple times

use "hg -v help grep" to show more info