hg cat [OPTION]... FILE...

output the current or given revision of files

    Print the specified files as they were at the given revision. If no
    revision is given, the parent of the working directory is used, or tip if
    no revision is checked out.

    Output may be to a file, in which case the name of the file is given using
    a format string. The formatting rules are the same as for the export
    command, with the following additions:

    "%s"          basename of file being printed
    "%d"          dirname of file being printed, or '.' if in repository root
    "%p"          root-relative path name of file being printed

    Returns 0 on success.


 -o --output FORMAT       print output to file with formatted name
 -r --rev REV             print the given revision
    --decode              apply any matching decode filter
 -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 cat" to show more info