I created my own target definition. It worked perfectly until now. Today I opened this target definition and got following error for all software sites I have there:
Unable to locate installable unit <unit name>
The target definition file looks like this:
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<?pde version="3.6"?>
<target name="indigo" sequenceNumber="20">
<locations>
<location includeAllPlatforms="false" includeMode="planner" includeSource="true" type="InstallableUnit">
<unit id="org.eclipse.zest.feature.group" version="1.3.0.v20110425-2050-67A18yF6F18CBD5A7N54242"/>
<unit id="org.eclipse.zest.sdk.feature.group" version="1.3.0.v20110425-2050-67C18COMPIAKSVKGQaRTQTiSN8WP"/>
<unit id="org.eclipse.zest.source.feature.group" version="1.3.0.v20110425-2050-67A18yF6F18CBD5A7N54242"/>
<repository location="http://download.eclipse.org/releases/indigo"/>
</location>
<location includeAllPlatforms="false" includeMode="planner" includeSource="true" type="InstallableUnit">
<unit id="org.eclipse.jdt.feature.group" version="3.7.2.v20120120-1414-7z8gFcuFMP7BW5XTz0jLTnz0l9B1"/>
<unit id="org.eclipse.jdt.source.feature.group" version="3.7.2.v20120120-1414-7z8gFcuFMP7BW5XTz0jLTnz0l9B1"/>
<unit id="org.eclipse.pde.source.feature.group" version="3.7.2.v20120120-1420-7b7rFUOFEx2Xnqafnpz0E--0"/>
<unit id="org.eclipse.platform.sdk" version="3.7.2.M20120208-0800"/>
<unit id="org.eclipse.rcp.id" version="3.7.2.M20120208-0800"/>
<unit id="org.eclipse.rcp.sdk.id" version="3.7.2.M20120208-0800"/>
<repository location="http://download.eclipse.org/eclipse/updates/3.7"/>
</location>
<location includeAllPlatforms="false" includeMode="planner" includeSource="true" type="InstallableUnit">
<unit id="org.eclipse.egit.feature.group" version="1.3.0.201202151440-r"/>
<unit id="org.eclipse.egit.source.feature.group" version="1.3.0.201202151440-r"/>
<unit id="org.eclipse.jgit.feature.group" version="1.3.0.201202151440-r"/>
<unit id="org.eclipse.jgit.source.feature.group" version="1.3.0.201202151440-r"/>
<repository location="http://download.eclipse.org/egit/updates"/>
</location>
<location path="${project_loc}/lib" type="Directory"/>
<location includeAllPlatforms="false" includeMode="planner" includeSource="true" type="InstallableUnit">
<unit id="org.tmatesoft.svnkit.feature.group" version="1.7.4.t20120412_2022"/>
<repository location="http://eclipse.svnkit.com/1.7.x"/>
</location>
<location path="${project_loc}/lib/deltapack" type="Profile"/>
</locations>
</target>
org.eclipse.pde.core
within.metadata/.plugins
. This would not require you to setup your workspace again. The next start of Eclipse might take some more time tough. – Sumptuary