Sometimes it is useful to construct a working copy that is made out
of a number of different checkouts. For example, you may want different
files or subdirectories to come from different locations in a repository,
or perhaps from different repositories altogether.
If you want every user to have the same layout, you can define the
svn:externals properties to pull in the specified
resource at the locations where they are needed.
Let's say you check out a working copy of
/project1 to
D:\dev\project1.
Select the folder D:\dev\project1,
right click and choose
→
from the context menu.
The Properties Dialog comes up. Then go to the Subversion tab.
There, you can set properties. Click Properties....
In the properties dialog, either double click on the
svn:externals if it already exists, or click
on the New... button and select
externals from the menu.
To add a new external, click the New...
and then fill in the required information in the shown dialog.
![[Caution]](/images/svn/caution.png) | Caution |
|---|
URLs must be properly escaped or they will not work, e.g. you must
replace each space with %20.
|
If you want the local path to include spaces or other special characters,
you can enclose it in double quotes, or you can use the \
(backslash) character as a Unix shell style escape character preceding any
special character. Of course this also means that you must use
/ (forward slash) as a path delimiter.
Note that this behaviour is new in Subversion 1.6 and will not work with
older clients.
![[Tip]](/images/svn/tip.png) | Use explicit revision numbers |
|---|
You should strongly consider using explicit revision numbers
in all of your externals definitions, as described above.
Doing so means
that you get to decide when to pull down a different snapshot
of external information, and exactly which snapshot to pull.
Besides the common sense aspect of not being surprised by
changes to third-party repositories that you might not have
any control over, using explicit revision numbers also means
that as you backdate your working copy to a previous
revision, your externals definitions will also revert to the
way they looked in that previous revision, which in turn means
that the external working copies will be updated to match they
way they looked back when your repository was
at that previous revision. For software projects, this could
be the difference between a successful and a failed build of
an older snapshot of your complex code base.
|
If the external project is in the same repository, any changes
you make there will be included in the commit list when
you commit your main project.
If the external project is in a different repository, any
changes you make to the external project will be notified
when you commit the main project, but you have to commit
those external changes separately.
If you use absolute URLs in svn:externals
definitions and you have to relocate your working copy (i.e.,
if the URL of your repository changes), then your externals
won't change and might not work anymore.
To avoid such problems, Subversion clients version 1.5 and
higher support relative external URLs. Four different methods
of specifying a relative URL are supported.
In the following examples, assume we have two repositories: one at
http://example.com/svn/repos-1
and another at
http://example.com/svn/repos-2.
We have a checkout of
http://example.com/svn/repos-1/project/trunk
into C:\Working and the svn:externals
property is set on trunk.
- Relative to parent directory
These URLs always begin with the string ../
for example:
../../widgets/foo common/foo-widget
This will extract
http://example.com/svn/repos-1/widgets/foo
into
C:\Working\common\foo-widget.
Note that the URL is relative to the URL of the directory with the
svn:externals property, not to the directory where
the external is written to disk.
- Relative to repository root
These URLs always begin with the string ^/
for example:
^/widgets/foo common/foo-widget
This will extract
http://example.com/svn/repos-1/widgets/foo
into
C:\Working\common\foo-widget.
You can easily refer to other repositories with the same
SVNParentPath (a common directory holding
several repositories). For example:
^/../repos-2/hammers/claw common/claw-hammer
This will extract
http://example.com/svn/repos-2/hammers/claw
into
C:\Working\common\claw-hammer.
- Relative to scheme
URLs beginning with the string // copy
only the scheme part of the URL. This is useful when the same hostname
must the accessed with different schemes depending upon network location;
e.g. clients in the intranet use http://
while external clients use svn+ssh://.
For example:
//example.com/svn/repos-1/widgets/foo common/foo-widget
This will extract
http://example.com/svn/repos-1/widgets/foo
or
svn+ssh://example.com/svn/repos-1/widgets/foo
depending on which method was used to checkout
C:\Working.
- Relative to the server's hostname
URLs beginning with the string / copy
the scheme and the hostname part of the URL, for example:
/svn/repos-1/widgets/foo common/foo-widget
This will extract
http://example.com/svn/repos-1/widgets/foo
into
C:\Working\common\foo-widget.
But if you checkout your working copy from another server at
svn+ssh://another.mirror.net/svn/repos-1/project1/trunk
then the external reference will extract
svn+ssh://another.mirror.net/svn/repos-1/widgets/foo.
You can also specify a peg revision for the URL if required.
If you need more information how TortoiseSVN
handles Properties read Section 4.17, “Project Settings”.
To find out about different methods of accessing common sub-projects
read Section B.6, “Include a common sub-project”.
As of Subversion 1.6 you can add single file externals to
your working copy using the same syntax as for folders.
However, there are some restrictions.
The path to the file external must place the file in an existing
versioned folder. In general it makes most sense to place the file
directly in the folder that has svn:externals
set, but it can be in a versioned sub-folder if necessary.
By contrast, directory externals will automatically create any
intermediate unversioned folders as required.
The URL for a file external must be in the same repository as the URL
that the file external will be inserted into; inter-repository file
externals are not supported.
A file external behaves just like any other versioned file in many respects,
but they cannot be moved or deleted using the normal commands; the
svn:externals property must be modified instead.
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