revert: "perf(fish): Skip unnecessary indirection in starship init fish" (starship#6326)

Revert "perf(fish): Skip unnecessary indirection in starship init fish (starship#6253)"

This reverts commit 798f640.

Author: davidkna

src/init/mod.rs

@@ -156,7 +156,11 @@ pub fn init_stub(shell_name: &str) -> io::Result<()> {
             starship.sprint_posix()?
         ),
         "zsh" => print_script(ZSH_INIT, &starship.sprint_posix()?),
-        "fish" => print_script(FISH_INIT, &starship.sprint_posix()?),
+        "fish" => print!(
+            // Fish does process substitution with pipes and psub instead of bash syntax
+            r#"source ({} init fish --print-full-init | psub)"#,
+            starship.sprint_posix()?
+        ),
         "powershell" => print!(
             r#"Invoke-Expression (& {} init powershell --print-full-init | Out-String)"#,
             starship.sprint_pwsh()?