Define fish function, ptree

Get all pstree outputs for a given process name.

Usage:
```fish
> ptree ssh-agent
```

I'm unsure if I like home-managers; I'd prefer defining this functions in a
functions.fish file for a few reasons:
- I like syntax highlighting.
- home-manager compiles this into poorly formatted fish code.

1 files changed, 9 insertions, 0 deletions

diff --git a/configs/.config/nixpkgs/home.nix b/configs/.config/nixpkgs/home.nix
index 51e857b823b5..08dd489b9988 100644
--- a/configs/.config/nixpkgs/home.nix
+++ b/configs/.config/nixpkgs/home.nix
@@ -105,6 +105,15 @@
       sysust = "systemctl --user status";
     };
     promptInit = builtins.readFile ../fish/prompt.fish;
+    functions = {
+      ptree = {
+        body = ''
+          for pid in (pgrep $argv[1])
+            pstree -s -p $pid
+          end
+        '';
+      };
+    };
   };
 
   programs.fzf = rec {