fix 'vim' alias on 'vi'-only system

Despite the fact that user installed 'vim-enhanced' package, the alias
didn't stop notifying user that 'vim' is not installed till the shell
was restarted.

Newly, if /usr/bin/vim suddenly appears (vim-enhanced is freshly
installed) the alias is mostly no-op and vim is used directly.

On top of ^, if user touches the ~/.i-know-vim-is-vi file, 'vi' is
silently started instead of 'vim' without the warning.

Resolves: rhbz#1907800

vim.sh

@@ -1,3 +1,20 @@
+__vi_internal_vim_alias()
+(
+    # if user installs vim-enanced and alias is already set
+    test -f /usr/bin/vim && exec vim "$@"
+
+    # if user hates the "No vim found .." interrupting message
+    test -f "$HOME"/.i-know-vim-is-vi && exec vi "$@"
+
+    if [ -n "${ZSH_VERSION-}" ]; then
+        read -t 10 -s -k 1 '?No vim found, using vi, press ENTER to continue...' && echo ''
+    else
+        read -rep $'No vim found, using vi, press ENTER to continue...\n' -n1 -t 10 -s
+    fi
+    exec vi "$@"
+)
+
+
 if [ -n "${BASH_VERSION-}" -o -n "${KSH_VERSION-}" -o -n "${ZSH_VERSION-}" ]; then
   # This will avoid user defined aliases and possibly stuff defined earlier in the PATH.
   case "$(command -v vim)-$(command -v vi)" in
@@ -8,11 +25,7 @@ if [ -n "${BASH_VERSION-}" -o -n "${KSH_VERSION-}" -o -n "${ZSH_VERSION-}" ]; th
         ;;
     -/usr/bin/vi)
         # apply only if founded vi is in expected dir from distro
-        if [ -n "${ZSH_VERSION-}" ]; then
+        alias vim=__vi_internal_vim_alias
-          alias vim="read -t 10 -s -k 1 '?No vim found, using vi, press ENTER to continue...' && echo '' && vi"
-        else
-          alias vim="read -rep $'No vim found, using vi, press ENTER to continue...\n' -n1 -t 10 -s && vi"
-        fi
         ;;
   esac
 fi