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, 27 insertions, 0 deletions

diff --git a/functions/check_install.fish b/functions/check_install.fish
new file mode 100644
index 0000000..4c5da6c
--- /dev/null
+++ b/functions/check_install.fish
@@ -0,0 +1,27 @@
+function check_install -a tool -a package
+
+if test (count $argv) -lt 1
+  return 1
+end
+
+if command -sq $tool
+  return 0
+end
+
+if not ask "$tool doesn't seem to be installed. Attempt to install it?"
+  return 1
+end
+
+if test -z $package
+  set package $tool
+end
+
+pkgadd $package || return 1
+
+if not command -sq $tool
+  return 1
+end
+
+return 0
+
+end