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<html lang="en">
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<title>ECB - the Emacs Code Browser</title>
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<p>
Node:<a name="Identifying%20backends">Identifying backends</a>,
Next:<a rel=next accesskey=n href="Checking-the-state.html#Checking%20the%20state">Checking the state</a>,
Previous:<a rel=previous accesskey=p href="Version-control-support.html#Version-control%20support">Version-control support</a>,
Up:<a rel=up accesskey=u href="Version-control-support.html#Version-control%20support">Version-control support</a>
<hr><br>
<h4>How ECB identifies the VC-backend of a dir</h4>
<p>ECB tries all functions added as identify-backend-funtions to the
option <code>ecb-vc-supported-backends</code> until one of them returns not
<code>nil</code> but a symbol which identifies the backend (e.g.
<code>CVS</code>). After this check ECB stores the result of this check
(i.e. either the identified backend or the fact that the directory is
not managed by a VC-system) for that directory in a special cache, so
the identify-backend-process will be performed only once per
directory. If for a directory a VC-backend could be identified ECB
stores not only the backend itself for that directory but also the
associated check-state-function defined in
<code>ecb-vc-supported-backends</code> (see <a href="Checking-the-state.html#Checking%20the%20state">Checking the state</a>).
<p>You can add arbitrary functions to this options as long as they get one
directory-argument and return either nil or a backend-symbol. Per
default ECB offers the following functions to identify the VC-backend
CVS, RCS, SCCS or Subversion<a rel=footnote href="#fn-1"><sup>1</sup></a>:
<dl>
<dt><code>ecb-vc-dir-managed-by-CVS DIRECTORY</code>
<dd>Return <code>CVS</code> if DIRECTORY is managed by CVS. nil if not.
<p>This function tries to be as smart as possible: First it checks if
DIRECTORY is managed by CVS by checking if there is a subdir
<code>CVS</code>. If no then nil is returned. If yes then for GNU Emacs it
takes into account the value of <code>vc-cvs-stay-local</code>: If t then
just return <code>CVS</code>. Otherwise ECB checks the root repository if it
is a remote repository. If not just <code>CVS</code> is returned. If a
remote repository it checks if the value of <code>vc-cvs-stay-local</code>
is a string and matches the host of that repository. If yes then just
<code>CVS</code> is returned. If not then ECB checks if that host is
currently accessible by performing a ping. If accessible <code>CVS</code> is
returned otherwise nil. This has the advantage that ECB will not be
blocked by trying to get the state from a remote repository while the
host is not accessible (e.g. because the user works offline).
<p>Special remark for XEmacs: XEmacs has a quite outdated VC-package
which has no option <code>vc-cvs-stay-local</code> so the user can not work
with remote CVS-repositories if working offline for example. So if
there is no option <code>vc-cvs-stay-local</code> then ECB performs always
the repository check mentioned above.
<br><dt><code>ecb-vc-dir-managed-by-RCS DIRECTORY</code>
<dd>Return <code>RCS</code> if DIRECTORY is managed by RCS. nil if not.
<br><dt><code>ecb-vc-dir-managed-by-SCCS DIRECTORY</code>
<dd>Return <code>SCCS</code> if DIRECTORY is managed by SCCS. nil if not.
<br><dt><code>ecb-vc-dir-managed-by-SVN DIRECTORY</code>
<dd>Return <code>SVN</code> if DIRECTORY is managed by Subversion. nil if not.
Returns always nil if the library vc-svn.el can not be found.
</dl>
<p>If ECB should support another VC-backend than CVS, RCS, SCCS or
Subversion you have to write your own identify-backend-funtion for the
used VC-backend (e.g. Clearcase)!
<h5>Special remarks for XEmacs</h5>
<p>XEmacs contains only a quite outdated VC-package, especially there is
no backend-independent check-vc-state-function available (like
<code>vc-state</code> for GNU Emacs). Only for CVS a check-vc-state-function
is available: <code>vc-cvs-status</code>. Therefore ECB adds per default
only support for CVS and uses <code>ecb-vc-managed-by-CVS</code> rsp.
<code>vc-cvs-status</code>. See also <a href="Known-VC-problems.html#Known%20VC-problems">Known VC-problems</a>!
<hr><h4>Footnotes</h4>
<ol type="1">
<li><a name="fn-1"></a>
<p>For this the most recent version
of the VC-package (incl. the library vc-svn.el) is needed - as
contained in CVS Emacs</p>
</ol><hr>
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