Ticket #4726: add mc-wrapper for fish shell

[krobelus]

fish shell occasionally gets bug reports from mc users, so there are definitely
some mc+fish users.

But none of them has noticed the lack of "/usr/libexec/mc/mc-wrapper.fish".

That file is supposed to define an alias that behaves like mc except that,
after mc exits, it will change fish's directory to the one last used by mc.

Users need to source this manually; if this is the behavior that most people
expect, we should make it the default (for example by shipping this function
with fish).

For now, add it to mc, which shouldn't break anyone even if fish decides to
add this as well.

Note that fish does not do word splitting, so variable expansions usually
don't need to be quoted.

Tested as follows:

$ make install
$ type mc
mc is /home/johannes/.local/bin/mc
$ source /home/johannes/.local/libexec/mc/mc.fish
$ type mc
mc is a function with definition
# Defined in /home/johannes/.local/libexec/mc/mc.fish @ line 1
function mc --description 'Visual shell for Unix-like systems - fish wrapper'
	source /home/johannes/.local/libexec/mc/mc-wrapper.fish $argv
end
mc
# navigate somewhere, press F10 to exit

Co-authored-by: Jarkko Sakkinen jarkko.sakkinen@iki.fi

Closes #4726

Signed-off-by: Johannes Altmanninger aclopte@gmail.com

[krobelus]

I didn't notice the build was broken because I had a stale contrib/Makefile locally.
Will fix. Normally I'd run git clean -dxn but I have some files I want to keep..
(make clean and make distclean still leave behind some stuff..)

[zyv]

In light of the discussion in #4726, I reverted my changes that silenced mc return code. I also added a comment to the wrappers to that effect.

[krobelus]

this will not actually propagate the exit code beyond line 13.
If we do want to propagate it (which seems like a good idea),
then we should be doing something like this (untested)
but probably for all shells

diff --git a/contrib/mc-wrapper.sh.in b/contrib/mc-wrapper.sh.in
index 399b38a892..1a8200b5de 100644
--- a/contrib/mc-wrapper.sh.in
+++ b/contrib/mc-wrapper.sh.in
@@ -6,7 +6,8 @@
 	MC_PWD_FILE="`mktemp "/tmp/mc.pwd.XXXXXX"`"
 fi
 
-@bindir@/mc -P "$MC_PWD_FILE" "$@" || true
+MC_STATUS=0
+@bindir@/mc -P "$MC_PWD_FILE" "$@" || MC_STATUS=$?
 
 if test -r "$MC_PWD_FILE"; then
 	MC_PWD="`cat "$MC_PWD_FILE"`"
@@ -18,3 +19,4 @@
 
 rm -f "$MC_PWD_FILE"
 unset MC_PWD_FILE
+eval "unset MC_STATUS; exit $MC_STATUS"

[krobelus]

I guess the comment was written assuming set -e, which is not the usual behavior, and even in that case we want to clean up.. though that's an edge case of an edge case

[krobelus]

FWIW I intentionally did not include the fish lines in this commit because they belong in the commit that adds the referenced fish files.
Of course the advantage from the separate commit is fairly small here so both could be combined into a single commit also.