Best effort dependency resolution

Add a new check_install function that checks if a tool is installed and
tries to install it on a best effort basic. Modify all scripts that
benefit from it. Small indentation and correctness fixes.

	modified:   functions/7za.fish
	modified:   functions/alert.fish
	new file:   functions/check_install.fish
	modified:   functions/lscmd.fish
	modified:   functions/rchmod.fish
	modified:   functions/renlow.fish
	modified:   functions/rlsxattr.fish
	modified:   functions/rsdos.fish
	modified:   functions/rsmac.fish
	modified:   functions/rsxattr.fish
	modified:   functions/uz.fish

1 files changed, 1 insertions, 2 deletions

diff --git a/functions/uz.fish b/functions/uz.fish
index b23780f..1611157 100644
--- a/functions/uz.fish
+++ b/functions/uz.fish
@@ -5,7 +5,7 @@ if test (count $argv) -lt 1
   return 1
 end
 
-if not command -sq bsdtar
+if not check_install 'bsdtar' 'libarchive'
   echo "Can't fint bsdtar."
   return 1
 end
@@ -23,4 +23,3 @@ for archive in $argv
 end
 
 end
-