Steps to reproduce:

1. Install git plugin
2. Create new job, choose any name, type free-style
3. Choose a git source code repository, enter an invalid url, click add
4. Click save at the bottom, an unhandled exception occurs and a 500 is returned with the stacktrace

I've noticed that other fields nicely detect errors as soon as they lose focus and show a handy message. Would it be possible to do that here?

Here are the log messages that get printed to the hudson log. The stack trace is the same as the one that is shown to the user:

[webapp 2010/03/09 18:36:30] - Error while serving http://localhost:8080/job/argablarg/configSubmit
java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.kohsuke.stapler.Function$InstanceFunction.invoke(Function.java:169)
at org.kohsuke.stapler.Function.bindAndInvoke(Function.java:101)
at org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:54)
at org.kohsuke.stapler.MetaClass$1.doDispatch(MetaClass.java:74)
at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:30)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:519)
at org.kohsuke.stapler.MetaClass$6.doDispatch(MetaClass.java:180)
at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:30)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:519)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:435)
at org.kohsuke.stapler.Stapler.service(Stapler.java:123)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:45)
at winstone.ServletConfiguration.execute(ServletConfiguration.java:249)
at winstone.RequestDispatcher.forward(RequestDispatcher.java:335)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:378)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:94)
at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:86)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:47)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:164)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
at winstone.RequestDispatcher.forward(RequestDispatcher.java:333)
at winstone.RequestHandlerThread.processRequest(RequestHandlerThread.java:244)
at winstone.RequestHandlerThread.run(RequestHandlerThread.java:150)
at java.lang.Thread.run(Thread.java:637)
Caused by: hudson.plugins.git.GitException: Error creating repositories
at hudson.plugins.git.GitSCM$DescriptorImpl.newInstance(GitSCM.java:800)
at hudson.plugins.git.GitSCM$DescriptorImpl.newInstance(GitSCM.java:730)
at hudson.model.Descriptor.newInstance(Descriptor.java:396)
at hudson.scm.SCMS.parseSCM(SCMS.java:66)
at hudson.model.AbstractProject.submit(AbstractProject.java:1489)
at hudson.maven.MavenModuleSet.submit(MavenModuleSet.java:702)
at hudson.model.Job.doConfigSubmit(Job.java:1005)
at hudson.model.AbstractProject.doConfigSubmit(AbstractProject.java:547)
... 35 more
Caused by: java.net.URISyntaxException: Cannot parse Git URI-ish: invalid
at org.spearce.jgit.transport.URIish.initializeFromString(URIish.java:115)
at org.spearce.jgit.transport.URIish.<init>(URIish.java:82)
at org.spearce.jgit.transport.RemoteConfig.<init>(RemoteConfig.java:149)
at org.spearce.jgit.transport.RemoteConfig.getAllRemoteConfigs(RemoteConfig.java:106)
at hudson.plugins.git.GitSCM$DescriptorImpl.newInstance(GitSCM.java:796)
... 42 more

[Winstone 2010/03/09 18:36:30] - Untrapped Error in Servlet
javax.servlet.ServletException: hudson.plugins.git.GitException: Error creating repositories
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:554)
at org.kohsuke.stapler.MetaClass$6.doDispatch(MetaClass.java:180)
at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:30)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:519)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:435)
at org.kohsuke.stapler.Stapler.service(Stapler.java:123)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:45)
at winstone.ServletConfiguration.execute(ServletConfiguration.java:249)
at winstone.RequestDispatcher.forward(RequestDispatcher.java:335)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:378)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:94)
at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:86)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:47)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:164)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
at winstone.RequestDispatcher.forward(RequestDispatcher.java:333)
at winstone.RequestHandlerThread.processRequest(RequestHandlerThread.java:244)
at winstone.RequestHandlerThread.run(RequestHandlerThread.java:150)
at java.lang.Thread.run(Thread.java:637)
Caused by: hudson.plugins.git.GitException: Error creating repositories
at hudson.plugins.git.GitSCM$DescriptorImpl.newInstance(GitSCM.java:800)
at hudson.plugins.git.GitSCM$DescriptorImpl.newInstance(GitSCM.java:730)
at hudson.model.Descriptor.newInstance(Descriptor.java:396)
at hudson.scm.SCMS.parseSCM(SCMS.java:66)
at hudson.model.AbstractProject.submit(AbstractProject.java:1489)
at hudson.maven.MavenModuleSet.submit(MavenModuleSet.java:702)
at hudson.model.Job.doConfigSubmit(Job.java:1005)
at hudson.model.AbstractProject.doConfigSubmit(AbstractProject.java:547)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.kohsuke.stapler.Function$InstanceFunction.invoke(Function.java:169)
at org.kohsuke.stapler.Function.bindAndInvoke(Function.java:101)
at org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:54)
at org.kohsuke.stapler.MetaClass$1.doDispatch(MetaClass.java:74)
at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:30)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:519)
... 25 more
Caused by: java.net.URISyntaxException: Cannot parse Git URI-ish: invalid
at org.spearce.jgit.transport.URIish.initializeFromString(URIish.java:115)
at org.spearce.jgit.transport.URIish.<init>(URIish.java:82)
at org.spearce.jgit.transport.RemoteConfig.<init>(RemoteConfig.java:149)
at org.spearce.jgit.transport.RemoteConfig.getAllRemoteConfigs(RemoteConfig.java:106)
at hudson.plugins.git.GitSCM$DescriptorImpl.newInstance(GitSCM.java:796)
... 42 more