Let TeXFiles.py handle symbolic links.

Nix (https://nixos.org) is a Unix package manager, which can be used to
install LaTeX on macOS. A peculiarity of Nix is that all packages are
installed into separate directories and the actual directory tree is
then constructed via symlinks.

This interacts badly with the way LyX currently detects files in the
TeX setup, because TeXFiles.py does not follow symlinks. Therefore,
almost nothing is found when using LyX together with Nix’ LaTeX.

Patch from Michael Roitzsch.

lib/CREDITS

@@ -503,6 +503,9 @@
 @bBernhard Roider
 @iE-mail: bernhard.roider () sonnenkinder ! org
    Various bug fixes
+@bMichael Roitzsch
+@iE-mail: reactorcontrol () icloud ! com
+   Fixes for the Nix package manager
 @bJim Rotmalm
 @iE-mail: jim.rotmalm () gmail ! com
    Swedish translation

lib/generate_contributions.py

@@ -1679,6 +1679,14 @@ contributors = [
                  "29 January 2007",
                  u"Various bug fixes"),
 
+     contributor(u"Michael Roitzsch",
+                 "reactorcontrol () icloud ! com",
+                 "GPL",
+                 "Re: TeXFiles.py compatibility with Nix on macOS",
+                 "m=156146891826580",
+                 "25 June 2019",
+                 u"Fixes for the Nix package manager"),
+
      contributor(u"Jim Rotmalm",
                  "jim.rotmalm () gmail ! com",
                  "GPL",

lib/scripts/TeXFiles.py

@@ -116,7 +116,17 @@ for type in types:
         if not os.path.isdir(dir):
             continue
         # walk down the file hierarchy
-        for root,path,files in os.walk(dir):
+        visited = set()
+        for root,dirs,files in os.walk(dir, followlinks=True):
+            # prevent inifinite recursion
+            recurse = []
+            for dir in dirs:
+                st = os.stat(os.path.join(root, dir))
+                key = st.st_dev, st.st_ino
+                if key not in visited:
+                    visited.add(key)
+                    recurse.append(dir)
+            dirs[:] = recurse
             # check file type
             for file in files:
                 if len(file) > 4 and file[-4:] == file_ext: