Add file search to find command

[vinc]

This PR implement file search in find and rename it --file <pattern> instead of --name <pattern> where <pattern> allow globbing like the shell. In --line <pattern> it is a standard regular expression.

By default find will be equivalent to find "$DIR" --file "*" instead of find --help.

[vinc]

[vinc]

It should be possible to do find / --file "*.lsp" --line "print" to recursively search a line pattern inside files matching a file pattern in the path.

It could also be possible to search in more than one path.

[vinc]

The find.png screenshot in the doc is not valid anymore because the regex syntax must be escaped since #558 and we introduced a new file in #618 that matches the line pattern in the example.

[vinc]

New screenshot for the documentation:

[vinc]

We can now use both --file and --line to filter in which files we want to search the given lines:

~
> find /tmp --line "list"
/tmp/alice.txt
63: was no one to listen to her, still it was good practice to say it over)
71: there WAS no one listening, this time, as it didn't sound at all the

/tmp/lisp/doc.lsp
9:     (if (nil? s) "" (str " " (if (list? s) (str/join s " ") s))) # args

~
> find /tmp --file "*.lsp" --line "list"
/tmp/lisp/doc.lsp
9:     (if (nil? s) "" (str " " (if (list? s) (str/join s " ") s))) # args

And the code has been refactored to be DRY.

[vinc]

Running find lisp inside /tmp would print files with a relative path starting with lisp/ but running find inside /tmp/lisp would print files with an absolute path starting with /tmp/lisp/. This inconsistency is now fixed:

~
> find /tmp/lisp
/tmp/lisp/colors.lsp
/tmp/lisp/doc.lsp
/tmp/lisp/factorial.lsp
/tmp/lisp/fibonacci.lsp
/tmp/lisp/geotime.lsp
/tmp/lisp/pi.lsp
/tmp/lisp/sum.lsp
/tmp/lisp/tak.lsp

~
> /tmp/lisp

/tmp/lisp
> find
colors.lsp
doc.lsp
factorial.lsp
fibonacci.lsp
geotime.lsp
pi.lsp
sum.lsp
tak.lsp