Add support for Breezy (brz) as alternative Bazaar implementation

The original Bazaar implementation (bzr) only runs on Python 2, but
there is a fork known as Breezy (brz) that has been ported to Python 3.

To support environments without Python 2, allow using Breezy:

* Add a setting 'bazaar-command' that specifies which command to run

* Set the default based on a path search, preferring 'bzr' but using
  'brz' if only 'brz' is found

* Implement a similar fallback in the test setup for Bazaar import

* Update README to mention Breezy as an alternative.  The
  'fastimport' extension is included in it rather than being a
  separate package.

Closes #3.

1 files changed, 27 insertions, 4 deletions

diff --git a/lorry b/lorry
index 90257b1..0318ef8 100755
--- a/lorry
+++ b/lorry
@@ -26,6 +26,7 @@ from datetime import datetime
 import shutil
 import traceback
 import functools
+import stat
 
 import yaml
 
@@ -52,6 +53,22 @@ def quote_url(url):
     return ''.join([transl(x) for x in url])
 
 
+def find_exec_in_path(name):
+    for dir_name in os.environ['PATH'].split(os.pathsep):
+        file_name = os.path.join(dir_name, name)
+        try:
+            file_stat = os.stat(file_name)
+        except OSError:
+            continue
+        if stat.S_ISREG(file_stat.st_mode) and file_stat.st_mode & 0o111:
+            return file_name
+    return None
+
+
+def find_bazaar_command():
+    return find_exec_in_path('bzr') or find_exec_in_path('brz')
+
+
 class Lorry(cliapp.Application):
 
     def add_settings(self):
@@ -101,6 +118,10 @@ class Lorry(cliapp.Application):
         self.settings.string_list(['push-option'],
                                   "option for 'git push' to pass to the "
                                   'remote server')
+        self.settings.string(['bazaar-command'],
+                             'command used to access Bazaar repositories',
+                             metavar='COMMAND',
+                             default=find_bazaar_command())
 
     def process_args(self, args):
         status = 0
@@ -334,11 +355,13 @@ class Lorry(cliapp.Application):
         self.run_program(argv, cwd=gitdir, env=env)
 
     def gitify_bzr(self, project_name, dirname, gitdir, spec):
+        bzr = self.settings['bazaar-command']
+
         bzrdir = os.path.join(dirname, 'bzr')
         # check if repo exists
         if not os.path.exists(bzrdir):
             self.progress('.. creating bzr repository')
-            self.run_program(['bzr', 'init-repo', '--no-trees', bzrdir])
+            self.run_program([bzr, 'init-repo', '--no-trees', bzrdir])
 
         if not os.path.exists(gitdir):
             self.progress('.. creating git repo')
@@ -360,12 +383,12 @@ class Lorry(cliapp.Application):
             if not os.path.exists(branchdir):
                 self.progress('.. doing initial bzr branch')
                 self.run_program(
-                    ['bzr', 'branch', '--quiet', '-Ossl.cert_reqs=none', 
+                    [bzr, 'branch', '--quiet', '-Ossl.cert_reqs=none',
                      address, branchdir])
             else:
                 self.progress('.. updating bzr branch')
                 self.run_program(
-                    ['bzr', 'pull', '--quiet', '-Ossl.cert_reqs=none', 
+                    [bzr, 'pull', '--quiet', '-Ossl.cert_reqs=none',
                      address],
                     cwd=branchdir)
 
@@ -375,7 +398,7 @@ class Lorry(cliapp.Application):
             branchdir = os.path.join(bzrdir, branch)
             self.progress('.. fast-exporting branch %s from bzr' % branch)
             exports[branch] = os.path.join(dirname, 'fast-export' + branch)
-            cmdline = ['bzr', 'fast-export', '--git-branch=' + branch, 
+            cmdline = [bzr, 'fast-export', '--git-branch=' + branch,
                        branchdir, exports[branch]]
             if os.path.exists(bzrmarks):
                 cmdline.append('--marks=' + bzrmarks)