fix(__load_completion): don't resolve symlinks to invoked command

This might make the path we install completions for different from the
invoked path so that the completion would fail to actually load after
setup.

The final path segment might also have a different name in the resolved
symlink, and we should not install it for the resolved name, because the
target's functionality might vary based on the invocation name.

Simply replacing the final path segment with the original basename could
yield a path that does not exist, even though the original invoked one
does.

#924 (comment)

Author: scop

bash_completion

@@ -2518,14 +2518,11 @@ __load_completion()
         backslash=\\
     fi
 
-    # Try to resolve real path to $cmd, and make it absolute
-    local ret realcmd="" origcmd=$cmd
-    if _comp_realcommand "$cmd"; then
-        realcmd=$ret
-        # Retain original basename, target $realcmd might behave differently
-        # depending on what it gets invoked as, so we should not install
-        # a completion for a different one for it. For example `busybox`.
-        cmd=${realcmd%/*}/$cmdname
+    # Resolve absolute path to $cmd
+    local ret pathcmd origcmd=$cmd
+    if pathcmd=$(type -P "$cmd"); then
+        _comp_abspath "$pathcmd"
+        cmd=$ret
     fi
 
     local -a dirs=()
@@ -2552,7 +2549,7 @@ __load_completion()
     fi
 
     # 3) From bin directories extracted from path to command, and $PATH
-    [[ $realcmd ]] && paths=("${realcmd%/*}") || paths=()
+    [[ $cmd == */* ]] && paths=("${cmd%/*}") || paths=()
     _comp_split -aF : paths "$PATH"
     for dir in "${paths[@]%/}"; do
         [[ $dir == ?*/@(bin|sbin) ]] &&