[mathiasrw]

Closes #791

Stacked on #804.

Change

The code of --js gets numbers. They start at 1.

Variable	The number of
$n	this file among the files found
$t	files found (the total)
$i	this file among the files with a match so far
$c	this file among the files changed so far
$m	this match in this file
$M	this match across all files so far

Each has cousins: with zeros in front as a string ($n0 has 2 digits, $n00 3, and so on to $n000000000 with 10), and with a space at the end ($n_, $n00_).

> rexreplace '^.*$' '"photo-" + $n00 + ext' '*.jpg' --rename --js --sort modified
photo-001.jpg
photo-002.jpg

• The variables are made by code put in front of the code of the user.
• A run that uses $i, $c, $m or $M handles the files one at a time, in the order of --sort, so the numbers are the same on every run.
• $m and $M make the code run once per match, like $0 and $1.
• $i and $c are only different when a match gives the same text: the file has a match, but is not changed.
• With € the shell does not get in the way: €n00.

Tests

yarn test-ci passes: the demo on Node and Bun (with €n00), and 1016 Bun tests. test/fix/791.test.js is new. Its test with 30 files fails when the run is not made to go one file at a time.