fish_add_path: Don't resolve symlinks

The case for symlinked directories being duplicated a lot isn't there,
but there *is* a usecase for adding the symlink rather than the
target, and that's homebrew.

E.g. homebrew installs ruby into /usr/local/Cellar/ruby/2.7.1_2/bin,
and links to it from /usr/local/opt/ruby/bin. If we add the target, we
would miss updates.

Having path entries that point to the same location isn't a big
problem - it's a path lookup, so it takes a teensy bit longer. The
canonicalization is mainly so paths don't end up duplicated via weird
spelling and so relative paths can be used.

doc_src/cmds/fish_add_path.rst

@@ -20,7 +20,7 @@ Description
 
 It is (by default) safe to use ``fish_add_path`` in config.fish, or it can be used once, interactively, and the paths will stay in future because of :ref:`universal variables <variables-universal>`. This is a "do what I mean" style command, if you need more control, consider modifying the variable yourself.
 
-Components are normalized by :ref:`realpath <cmd-realpath>`. This means that trailing slashes are ignored and symlinks are resolved, and relative paths are made absolute. If a component already exists, it is not added again and stays in the same place unless the ``--move`` switch is given.
+Components are normalized by :ref:`realpath <cmd-realpath>`. This means that trailing slashes are ignored and relative paths are made absolute (but symlinks are not resolved). If a component already exists, it is not added again and stays in the same place unless the ``--move`` switch is given.
 
 Components are added in the order they are given, and they are prepended to the path unless ``--append`` is given (if $fish_user_paths is used, that means they are last in $fish_user_paths, which is itself prepended to $PATH, so they still stay ahead of the system paths).
 
@@ -64,3 +64,6 @@ Example
    # I want to add the bin/ directory of my current $PWD (say /home/nemo/)
    > fish_add_path -v bin/
    set fish_user_paths /home/nemo/bin /usr/bin /home/nemo/.local/bin
+
+   # I have installed ruby via homebrew
+   fish_add_path /usr/local/opt/ruby/bin

doc_src/cmds/realpath.rst

@@ -21,4 +21,4 @@ If a ``realpath`` command exists, it will be preferred, so if you want to use th
 
 The following options are available:
 
-- ``-s`` or ``--no-symlink``: Don't resolve symlinks, only make paths absolute, squash multiple slashes and remove trailing slashes.
+- ``-s`` or ``--no-symlinks``: Don't resolve symlinks, only make paths absolute, squash multiple slashes and remove trailing slashes.

share/functions/fish_add_path.fish

@@ -41,7 +41,7 @@ function fish_add_path --description "Add paths to the PATH"
         # We could add a non-canonical version of the given path if no duplicate exists, but tbh that's a recipe for disaster.
 
         # realpath complains if a parent directory does not exist, so we silence stderr.
-        set -l p (builtin realpath -- $path 2>/dev/null)
+        set -l p (builtin realpath -s -- $path 2>/dev/null)
 
         # Ignore non-existing paths
         test -d "$p"; or continue

tests/checks/fish_add_path.fish

@@ -30,19 +30,20 @@ echo $status
 # CHECK: 1
 functions --erase checkpath
 
-# Not adding a link either
+# Add a link to the same path.
 fish_add_path -v $tmpdir/link
+# CHECK: set fish_user_paths {{.*}}/link {{.*}}/bin
 echo $status
-# CHECK: 1
+# CHECK: 0
 
 fish_add_path -a $tmpdir/sbin
 # Not printing anything because it's not verbose, the /sbin should be added at the end.
 string replace -- $tmpdir '' $fish_user_paths | string join ' '
-# CHECK: /bin /sbin
+# CHECK: /link /bin /sbin
 
 fish_add_path -m $tmpdir/sbin
 string replace -- $tmpdir '' $fish_user_paths | string join ' '
-# CHECK: /sbin /bin
+# CHECK: /sbin /link /bin
 
 set -l oldpath "$PATH"
 fish_add_path -nP $tmpdir/etc | string replace -- $tmpdir ''