gnulib-tool.py: Reduce code duplication.

* pygnulib/constants.py (relinverse): New function.
* pygnulib/GLEmiter.py (GLEmiter.po_Makevars,
GLEmiter.tests_Makefile_am): Use it.
* pygnulib/GLTestDir.py (GLTestDir.execute): Likewise.

3 files changed, 21 insertions, 24 deletions

diff --git a/pygnulib/GLEmiter.py b/pygnulib/GLEmiter.py
index c0fd053077..4c8f0d90f2 100644
--- a/pygnulib/GLEmiter.py
+++ b/pygnulib/GLEmiter.py
@@ -42,6 +42,7 @@ __copyright__ = constants.__copyright__
 #===============================================================================
 TESTS = constants.TESTS
 joinpath = constants.joinpath
+relinverse = constants.relinverse
 isfile = os.path.isfile
 normpath = os.path.normpath
 
@@ -390,13 +391,7 @@ class GLEmiter(object):
         emit = ''
         pobase = self.config['pobase']
         podomain = self.config['podomain']
-        top_subdir = ''
-        source = '%s/' % os.path.normpath(pobase)
-        if os.path.sep in source:
-            for directory in source.split(os.path.sep):
-                if directory != '':
-                    top_subdir += '../'
-        top_subdir = os.path.normpath(top_subdir)
+        top_subdir = relinverse(pobase)
         emit += "## DO NOT EDIT! GENERATED AUTOMATICALLY!\n"
         emit += "%s\n" % self.copyright_notice()
         emit += "# Usually the message domain is the same as the package name.\n"
@@ -941,13 +936,8 @@ AC_DEFUN([%V1%_LIBSOURCES], [
         else:  # if not for_test
             edit_check_PROGRAMS = False
 
-        # Calculate testsbase_inverse
-        counter = int()
-        testsbase_inverse = ''
-        while counter < len(testsbase.split('/')):
-            testsbase_inverse += '../'
-            counter += 1
-        testsbase_inverse = os.path.normpath(testsbase_inverse)
+        # Compute testsbase_inverse
+        testsbase_inverse = relinverse(testsbase)
 
         # Begin the generation.
         emit += "## DO NOT EDIT! GENERATED AUTOMATICALLY!\n"
diff --git a/pygnulib/GLTestDir.py b/pygnulib/GLTestDir.py
index bf00099283..68cc5ce411 100644
--- a/pygnulib/GLTestDir.py
+++ b/pygnulib/GLTestDir.py
@@ -48,6 +48,7 @@ DIRS = constants.DIRS
 UTILS = constants.UTILS
 TESTS = constants.TESTS
 joinpath = constants.joinpath
+relinverse = constants.relinverse
 copyfile = constants.copyfile
 movefile = constants.movefile
 isdir = os.path.isdir
@@ -405,16 +406,7 @@ class GLTestDir(object):
                     file.write(emit)
                 # Viewed from the $testsbase subdirectory, $auxdir is different.
                 emit = ''
-                saved_auxdir = self.config['auxdir']
-                testsbase = '%s/' % os.path.normpath(testsbase)
-                counter = int()
-                auxdir = ''
-                finish = (len(testsbase.split('/')) - 1)
-                while counter < finish:
-                    auxdir += '../'
-                    counter += 1
-                auxdir = os.path.normpath(joinpath(auxdir, saved_auxdir))
-                testsbase = os.path.normpath(testsbase)
+                auxdir = os.path.normpath(joinpath(relinverse(testsbase), auxdir))
                 self.config.setAuxDir(auxdir)
                 # Create $testsbase/configure.ac.
                 emit += '# Process this file with autoconf '
diff --git a/pygnulib/constants.py b/pygnulib/constants.py
index ae27d8d41a..10e11623b4 100644
--- a/pygnulib/constants.py
+++ b/pygnulib/constants.py
@@ -299,6 +299,21 @@ def relconcat(dir1, dir2):
     return os.path.normpath(os.path.join(dir1, dir2))
 
 
+def relinverse(dir):
+    '''Compute the inverse of dir. Namely, a relative pathname consisting only
+    of '..' components, such that dir/relinverse = '.'.
+    dir must be a relative pathname.'''
+    if False:
+        # This should work too.
+        return relativize(dir, '.')
+    else:
+        inverse = ''
+        for component in dir.split('/'):
+            if component != '':
+                inverse += '../'
+        return os.path.normpath(inverse)
+
+
 def copyfile(src, dest):
     '''Copy file src to file dest. Like shutil.copy, but ignore errors e.g. on
     VFAT file systems.'''