root and rootalias don't sanitize the same way (trailing slash)

[elvanor]

I have thoroughly read the Reporting Bugs and Feature Requests wiki page.

Environment

• Unison version: 2.53.7
• Gentoo Linux, AMD
• ocaml version: 4.14.2
• TUI or GUI: GUI (does not matter)
• local, ssh, socket: local
• use of fsmonitor: Not sure (irrelevant)

Reproduction Recipe

Use root & rootalias. For instance my test profile is:

Unison preferences file

root = /mnt/data/games/amiga/
root = /tmp/amiga/
rootalias = //caradhras//mnt/data/games/amiga/ -> //gagaxxx//mnt/data/games/amiga/
rootalias = //caradhras//tmp/amiga/ -> //gagaxxx//tmp/amiga
logfile = /tmp/unison-test.log
watch = false
ignore = Path lost+found

Expected behavior vs actual behavior

If you run with UNISONLOCALHOSTNAME="caradhras" unison -showarchive, you will see that the caradhras hostname is not replaced by gagaxxx in the archive paths. This is because it uses root = /mnt/data/games/amiga (removed trailing slash) but rootalias = //caradhras//mnt/data/games/amiga/ (trailing slash present). So it does not match.