Prioritize Comsol installation found on search path.

There may be situations where multiple installations of the same Comsol
version exist on the same machine, but the (current) user wants to pick
the one which has a single-user license in their name. The easiest way
to do that is to just change that user's PATH variable once and for all.

Related discussion: #172

Author: john-hen

mph/discovery.py

@@ -11,14 +11,15 @@
 folder `.local` in the user's home directory is also searched to allow
 symbolic linking to a custom location.
 
-In a last step, we also run the shell command `where comsol` (on Windows)
+Additionally, we also run the shell command `where comsol` (on Windows)
 or `which comsol` (on Linux and macOS) to find a Comsol installation
 that isn't in a default location, but for which the Comsol executable
 was added to the executable search path.
 
 Note that duplicate installations will be ignored. That is, a Comsol
 installation found in a later step that reports the same version as one
 found in an earlier step will be ignored, regardless of install location.
+The one found on the search path, if any, will be prioritized.
 """
 
 from __future__ import annotations
@@ -232,7 +233,7 @@ def search_disk(architecture: str) -> list[Path]:
     return executables
 
 
-def lookup_comsol() -> Path | None:
+def search_path() -> Path | None:
     """Returns Comsol executable if found on the system's search path."""
 
     log.debug('Looking for Comsol executable on system search path.')
@@ -289,10 +290,14 @@ def find_backends() -> list[Backend]:
         raise NotImplementedError(error)
 
     # Look up `comsol` command as if run in terminal.
-    comsol = lookup_comsol()
+    comsol = search_path()
     if comsol:
         if comsol not in executables:
-            executables.append(comsol)
+            executables.insert(0, comsol)
+            # We put that Comsol executable first so that users have a way of
+            # prioritizing one Comsol installation over another. This makes
+            # sense for multiple installations of the same Comsol version, each
+            # with a single-user license for a different user.
         else:
             log.debug('Ignoring executable as it was previously found.')