git-build-recipe crashes

[Rod Smith]

I'm trying to test build recipes for git projects, as per http://blog.launchpad.net/cool-new-stuff/beta-test-git-recipes and https://help.launchpad.net/Packaging/SourceBuilds/GettingStarted. My recipe (certification-docs.recipe) is:

# git-build-recipe format 0.3 deb-version {debupstream}-0~{revno}
lp:certification-docs

The result when I try running it is:

$ git-build-recipe --allow-fallback-to-native certification-docs.recipe working-dir
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/gitbuildrecipe/recipe.py", line 300, in git_clone
    cmd, stderr=subprocess.STDOUT, universal_newlines=True)
  File "/usr/lib/python3.4/subprocess.py", line 620, in check_output
    raise CalledProcessError(retcode, process.args, output=output)
subprocess.CalledProcessError: Command '['git', '-c', 'url.https://git.launchpad.net/.insteadOf=lp:', 'clone', '-n', 'lp:certification-docs', 'working-dir/certification-docs']' returned non-zero exit status 128

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/bin/git-build-recipe", line 9, in <module>
    load_entry_point('git-build-recipe==0.1', 'console_scripts', 'git-build-recipe')()
  File "/usr/lib/python3/dist-packages/gitbuildrecipe/main.py", line 110, in main
    build_tree(base_branch, working_directory)
  File "/usr/lib/python3/dist-packages/gitbuildrecipe/recipe.py", line 484, in build_tree
    _build_inner_tree(base_branch, target_path)
  File "/usr/lib/python3/dist-packages/gitbuildrecipe/recipe.py", line 405, in _build_inner_tree
    pull_or_clone(base_branch, target_path)
  File "/usr/lib/python3/dist-packages/gitbuildrecipe/recipe.py", line 329, in pull_or_clone
    git_clone(base_branch.url, target_path)
  File "/usr/lib/python3/dist-packages/gitbuildrecipe/recipe.py", line 303, in git_clone
    raise CloneFailed(e.output)
gitbuildrecipe.recipe.CloneFailed: git clone failed:
Cloning into 'working-dir/certification-docs'...
fatal: No path specified. See 'man git-pull' for valid url syntax

This may well be a case of improper use (command line or .recipe file), but the Python crash dump isn't exactly a model of clarity. If this is an improper-use case, could it be detected and a helpful error message produced instead?

[Colin Watson (cjwatson)]

At present it is not in general possible to build from a private repository on Launchpad using git-build-recipe. This won't be possible until we have HTTPS access tokens for private repositories (as it happens I'm working on prerequisites for that right now, but it will take a while). You can do it locally by using git+ssh://git.launchpad.net/certification-docs rather than lp:certification-docs, but it isn't going to work as part of a recipe build on Launchpad for a while yet.

I agree that the error message lacks a certain something, and will see what I can do to improve that.