vifm: Add simple file and folder diff command

The newly added `:cmp` command can compare the contents of either two
files or two directories.

Works in two ways: If nothing is selected, compares the currently
hovered-over object with that in the other pane.
If things are selected, compares those instead.

terminal/.config/vifm/scripts/vifmdiff

@@ -0,0 +1,31 @@
+#!/bin/bash
+
+if [ $# != 2 ] ; then
+    echo 'Expected exactly two arguments'
+    exit 1
+fi
+
+if [ -f "$1" ] && [ -f "$2" ]; then
+    args=
+elif [ -d "$1" ] && [ -d "$2" ]; then
+    args='-r'
+else
+    if [ -f "$1" ]; then
+        type_of_1='file'
+    else
+        type_of_1='directory'
+    fi
+    if [ -f "$2" ]; then
+        type_of_2='file'
+    else
+        type_of_2='directory'
+    fi
+    echo "Arguments are of different type ($type_of_1/$type_of_2)"
+    exit 1
+fi
+
+if diff $args "$1" "$2" > /dev/null 2>&1; then
+    echo 'Equal'
+else
+    echo 'Not equal'
+fi

terminal/.config/vifm/vifmrc

@@ -297,6 +297,13 @@ nnoremap te :execute ':tree! | echo ":tree"'<cr>
 nnoremap tt t
 nnoremap ti :toggleicons<cr>
 
+" fzf movements
+nnoremap <space>f :fzf<cr>
+nnoremap <space>F :fzfhome<cr>
+nnoremap <space>c :fzfcd<cr>
+nnoremap <space>C :fzfcdhome<cr>
+nnoremap <space>w :grep<space>
+
 " external commands
 " extract currently selected file(s)
 noremap ,xx :!atool -x %f<cr>
@@ -309,13 +316,6 @@ noremap ,xz :!atool -a %c:r.zip %f<cr>
 " combine selected PDFs into single one (named output.pdf)
 noremap ,pc :!pdftk %f cat output output.pdf
 
-" fzf movements
-nnoremap <space>f :fzf<cr>
-nnoremap <space>F :fzfhome<cr>
-nnoremap <space>c :fzfcd<cr>
-nnoremap <space>C :fzfcdhome<cr>
-nnoremap <space>w :grep<space>
-
 " preview thumbnails of current folder
 " select thumbnails with m/M in nsxiv
 " to generate a filtered view on them
@@ -650,3 +650,12 @@ filetype * open
 "     vifm --server-name "$VIFM_SERVER_NAME" --remote +"cd '$PWD'"
 "
 " let $VIFM_SERVER_NAME = v:servername
+
+command! cmpinternal vifmdiff %a %S
+command! cmp : if expand('%%c') == expand('%%f')
+          \ |     echo expand('Comparing %%"c and %%"C:t ...')
+          \ |     cmpinternal %c %C
+          \ | else
+          \ |     echo expand('Comparing files: %%"f ...')
+          \ |     cmpinternal %f
+          \ | endif