I can imagine two channels of independent work inside.

I need pijul clean to remove U’s each other without respect. BTW, I know how to write a test scenario.

$ pijul init p1
$ cd p1
$ pijul fork main2
$ touch a 
$ pijul add a
$ pijul record -am.
Hash: HQQ7ZP5YGVZRVRFPRG33JDADAZVMOV3ILYOWDHKXYIAQBIXQ7Q7QC
# milestone 1
$ pijul channel switch main2
$ piju diff -su
# trash-a-like files
U a
U .ignore
$ touch b
$ pijul add b
$ pijul rec -am.
Hash: RVPCVUK7XLKPQGUWP3ZPAPHZSUU54KEOTOGHUR6RJGXGTQHCBWWAC
# milestone 2
$ pijul channel switch main
$ pijul diff -su
U b
U.ignore
$