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Description:

vcsrepomgr 4.2

The Python package vcs-repo-mgr provides a command line program and Python
API to perform common operations (in the context of packaging/deployment) on
version control repositories. It’s currently tested on Python 2.6, 2.7, 3.4,
3.5 and 3.6 on Linux and Mac OS X. Bazaar, Mercurial and Git repositories
are supported.

Installation
Usage

Updating repositories
Finding revision numbers/ids
Exporting revisions

Future improvements
Known issues

Problematic dependencies

Contact
License

Installation
The vcs-repo-mgr package is available on PyPI which means installation
should be as simple as:
$ pip install vcs-repo-mgr
There’s actually a multitude of ways to install Python packages (e.g. the per
user site-packages directory, virtual environments or just installing
system wide) and I have no intention of getting into that discussion here, so
if this intimidates you then read up on your options before returning to these
instructions ;-).
You will also need Bazaar, Mercurial and/or Git installed (depending on the
type of repositories you want to work with). Here’s how you install them on
Debian and Ubuntu based systems:
$ sudo apt-get install bzr mercurial git-core

Usage
There are two ways to use the vcs-repo-mgr package: As the command line
program vcs-tool and as a Python API. For details about the Python API
please refer to the API documentation available on Read the Docs. The
command line interface is described below.
Usage: vcs-tool [OPTIONS] [ARGS]
Command line program to perform common operations (in the context of
packaging/deployment) on version control repositories. Supports Bazaar,
Mercurial and Git repositories.
Supported options:

Option
Description

-r, --repository=REPOSITORY
Select a repository to operate on by providing the name of a repository
defined in one of the configuration files ~/.vcs-repo-mgr.ini and
/etc/vcs-repo-mgr.ini.
Alternatively the location of a remote repository can be given. The
location should be prefixed by the type of the repository (with a “+” in
between) unless the location ends in “.git” in which case the prefix is
optional.

--rev, --revision=REVISION
Select a revision to operate on. Accepts any string that’s supported by the
VCS system that manages the repository, which means you can provide branch
names, tag names, exact revision ids, etc. This option is used in
combination with the --find-revision-number, --find-revision-id and
--export options.
If this option is not provided a default revision is selected: “last:1” for
Bazaar repositories, “master” for git repositories and “default” (not
“tip”!) for Mercurial repositories.

--release=RELEASE_ID
Select a release to operate on. This option works in the same way as the
--revision option. Please refer to the vcs-repo-mgr documentation for
details on “releases”.
Although release identifiers are based on branch or tag names they
may not correspond literally, this is why the release identifier you
specify here is translated to a global revision id before being passed to
the VCS system.

-n, --find-revision-number
Print the local revision number (an integer) of the revision given with the
--revision option. Revision numbers are useful as a build number or when a
simple, incrementing version number is required. Revision numbers should
not be used to unambiguously refer to a revision (use revision ids for that
instead). This option is used in combination with the --repository and
--revision options.

-i, --find-revision-id
Print the global revision id (a string) of the revision given with the
--revision option. Global revision ids are useful to unambiguously refer to
a revision. This option is used in combination with the --repository and
--revision options.

--list-releases
Print the identifiers of the releases in the repository given with the
--repository option. The release identifiers are printed on standard
output (one per line), ordered using natural order comparison.

--select-release=RELEASE_ID
Print the identifier of the newest release that is not newer than
RELEASE_ID in the repository given with the --repository option.
The release identifier is printed on standard output.

-s, --sum-revisions
Print the summed revision numbers of multiple repository/revision pairs.
The repository/revision pairs are taken from the positional arguments to
vcs-repo-mgr.
This is useful when you’re building a package based on revisions from
multiple VCS repositories. By taking changes in all repositories into
account when generating version numbers you can make sure that your version
number is bumped with every single change.

--vcs-control-field
Print a line containing a Debian control file field and value. The field
name will be one of “Vcs-Bzr”, “Vcs-Hg” or “Vcs-Git”. The value will be the
repository’s remote location and the selected revision (separated by a “#”
character).

-u, --update
Create/update the local clone of a remote repository by pulling the latest
changes from the remote repository. This option is used in combination with
the --repository option.

-m, --merge-up
Merge a change into one or more release branches and the default branch.
By default merging starts from the current branch. You can explicitly
select the branch where merging should start using the --rev, --revision
and --release options.
You can also start by merging a feature branch into the selected release
branch before merging the change up through later release branches and the
default branch. To do so you pass the name of the feature branch as a
positional argument.
If the feature branch is located in a different repository you can prefix
the location of the repository to the name of the feature branch with a “#”
token in between, to delimit the location from the branch name.

-e, --export=DIRECTORY
Export the contents of a specific revision of a repository to a local
directory. This option is used in combination with the --repository and
--revision options.

-d, --find-directory
Print the absolute pathname of a local repository. This option is used in
combination with the --repository option.

-v, --verbose
Increase logging verbosity (can be repeated).

-q, --quiet
Decrease logging verbosity (can be repeated).

-h, --help
Show this message and exit.

The primary way to use the vcs-tool command requires you to create a
configuration file:
$ cat > ~/.vcs-repo-mgr.ini << EOF
[coloredlogs]
type = git
local = /tmp/coloredlogs
remote = git@github.com:xolox/python-coloredlogs.git
EOF
Because the -r, --repository option accepts remote repository locations
in addition to names it’s not actually required to create a configuration file.
Of course this depends on your use case(s).
Below are some examples of the command line interface. If you’re interested in
using the Python API please refer to the online documentation.

Updating repositories
If the configuration file defines a local and remote repository and the local
repository doesn’t exist yet it will be created the first time you update it:
$ vcs-tool --repository coloredlogs --update
2014-05-04 18:55:54 INFO Creating Git clone of git@github.com:xolox/python-coloredlogs.git at /tmp/coloredlogs ..
Cloning into bare repository '/tmp/coloredlogs'...
remote: Reusing existing pack: 96, done.
remote: Counting objects: 5, done.
remote: Compressing objects: 100% (5/5), done.
remote: Total 101 (delta 0), reused 0 (delta 0)
Receiving objects: 100% (101/101), 28.11 KiB, done.
Resolving deltas: 100% (44/44), done.
Later runs will pull the latest changes instead of performing a full clone:
$ vcs-tool --repository coloredlogs --update
2014-05-04 18:55:56 INFO Updating Git clone of git@github.com:xolox/python-coloredlogs.git at /tmp/coloredlogs ..
From github.com:xolox/python-coloredlogs
* branch HEAD -> FETCH_HEAD

Finding revision numbers/ids
Revision numbers are integer numbers that increment with every added revision.
They’re very useful during packaging/deployment:
$ vcs-tool --repository coloredlogs --revision master --find-revision-number
24
Revision ids (hashes) are hexadecimal strings that uniquely identify revisions.
They are useful to unambiguously refer to a revision and its history (e.g while
building a package you can embed the revision id as a hint about the origins of
the package):
$ vcs-tool --repository coloredlogs --revision master --find-revision-id
bce75c1eea88ebd40135cd45de716fe9591e348c

Exporting revisions
By default the repositories created by vcs-repo-mgr do not contain a working tree,
just the version control files (in Git terminology this is called a “bare
repository”). This has two reasons:

Bare repositories help conserve disk space. This is insignificant for small
repositories, but on large repositories it can make a noticeable difference.
Especially if you’re using a lot of them :-)
Bare repositories enforce the principle that the working tree shouldn’t be
used during packaging (instead you should export the tree at a specific
revision to a temporary directory and use that). This insistence on not
using the working tree during packaging has two reasons:

The working tree can contain files which are not under version control.
Such files should certainly not be included in a package
unintentionally.
If the working tree of a repository is used, this makes it impossible to
safely perform parallel builds from the same repository (the builds can
corrupt each other’s working tree).

This means that if you want to do something with the files in the repository
you have to export a revision to a (temporary) directory:
$ vcs-tool --repository coloredlogs --export /tmp/coloredlogs-snapshot
2014-05-04 19:17:24 INFO Exporting revision master of /tmp/coloredlogs to /tmp/coloredlogs-snapshot ..

$ ls -l /tmp/coloredlogs-snapshot
total 28K
drwxrwxr-x 2 peter peter 4.0K May 3 14:31 coloredlogs
drwxrwxr-x 3 peter peter 4.0K May 3 14:31 vim
-rw-rw-r-- 1 peter peter 1.1K May 3 14:31 LICENSE.txt
-rw-rw-r-- 1 peter peter 56 May 3 14:31 MANIFEST.in
-rw-rw-r-- 1 peter peter 5.4K May 3 14:31 README.rst
-rwxrwxr-x 1 peter peter 1.1K May 3 14:31 setup.py

Future improvements
This section is currently a “braindump” which means I haven’t committed to any
of these improvements, I’m just thinking out loud ;-).

Improve interactive repository selection
Two improvements for interactive usage of the vcs-tool program:

Automatically load a repository’s configuration when a pathname is given
that matches an entry in a configuration file (right now you need to give
the repository’s name in order to load its configuration).
Do the obvious thing when no repository is specified on the command line but
the working directory matches a configured repository.

Wildcard matching in configuration files
It might be interesting to support shell wildcard matching against local
directory names to apply a default configuration to a group of repositories?

Enable more extensive customization
Right now the version control commands are hard coded and not easy to
customize for those cases where the existing API gets you 90% of where you
want to be but makes that last 10% impossible. Technically this is already
possible through subclassing, but a more lightweight solution would
certainly be nice to have :-).

Known issues
This section documents known issues that users may run into.

Problematic dependencies
Bazaar and Mercurial are both written in Python and available on PyPI and as
such I included them in the installation requirements of vcs-repo-mgr,
because I couldn’t think of a good reason not to.
Adding support for Python 3 to vcs-repo-mgr made things more complicated
because Bazaar and Mercurial didn’t support Python 3, leading to installation
errors. To cope with this problem the Bazaar and Mercurial requirements were
made conditional on the Python version:

On Python 2 the Bazaar and Mercurial packages would be installed together
with vcs-repo-mgr.
On Python 3 the user was instead responsible for making sure that Bazaar and
Mercurial were installed (for example using system packages).

This works fine because vcs-repo-mgr only invokes Bazaar and Mercurial using
the command line interfaces so it doesn’t matter whether the version control
system is using the same version of Python as vcs-repo-mgr.
Since then the installation of the Bazaar package has started failing on PyPy,
unfortunately this time there is no reliable and backwards compatible way to
make the Bazaar dependency optional in wheel distributions due to bugs in
setuptools.
When I investigated support for environment markers that match Python
implementations (refer to the link above) I decided that instead of writing a
setup script full of nasty and fragile hacks I’d rather just drop official
(tested) support for PyPy, as silly as the reason for it may be.

Contact
The latest version of vcs-repo-mgr is available on PyPI and GitHub. The
documentation is hosted on Read the Docs and includes a changelog. For bug
reports please create an issue on GitHub. If you have questions, suggestions,
etc. feel free to send me an e-mail at peter@peterodding.com.

License
This software is licensed under the MIT license.
© 2018 Peter Odding.