just: make new bash completion test work from build

pkgs/by-name/ju/just/fix-just-path-in-tests.patch

@@ -0,0 +1,20 @@
+diff --git a/tests/completions/just.bash b/tests/completions/just.bash
+index 6d5c12c..13bff87 100755
+--- a/tests/completions/just.bash
++++ b/tests/completions/just.bash
+@@ -17,11 +17,13 @@ reply_equals() {
+   fi
+ }
+ 
++just() {
++  cargo run -- "$@"
++}
++
+ # --- Initial Setup ---
+ source "$1"
+ cd tests/completions
+-cargo build
+-PATH="$(git rev-parse --show-toplevel)/target/debug:$PATH"
+ exit_code=0
+ 
+ # --- Tests ---

pkgs/by-name/ju/just/package.nix

@@ -2,6 +2,7 @@
 , stdenv
 , fetchFromGitHub
 , rustPlatform
+, bashInteractive
 , coreutils
 , installShellFiles
 , libiconv
@@ -42,8 +43,16 @@ rustPlatform.buildRustPackage rec {
 
     # Return unchanged string.rs
     cp $TMPDIR/string.rs tests/string.rs
+
+    # For shell completion tests
+    export PATH=${bashInteractive}/bin:$PATH
+    patchShebangs tests
   '';
 
+  patches = [
+    ./fix-just-path-in-tests.patch
+  ];
+
   postBuild = ''
     cargo run --package generate-book