ENH: Teach pre-commit to reject content link with raw file
ENH: Teach pre-commit to reject content link with raw file

ExternalData content links represent their original data files in the
source tree.  It does not make sense to have both at once.  Reject
attempts to commit a file and content link with the same name.

Change-Id: Iec1573ca0dfa774dac053b899a382ca39ed44381

rhgong/itk-with-dom,biotrump/ITK,vfonov/ITK,itkvideo/ITK,blowekamp/ITK,atsnyder/ITK,stnava/ITK,atsnyder/ITK,heimdali/ITK,rhgong/itk-with-dom,Kitware/ITK,BlueBrain/ITK,atsnyder/ITK,GEHC-Surgery/ITK,zachary-williamson/ITK,LucasGandel/ITK,spinicist/ITK,jmerkow/ITK,zachary-williamson/ITK,eile/ITK,malaterre/ITK,richardbeare/ITK,paulnovo/ITK,CapeDrew/DCMTK-ITK,PlutoniumHeart/ITK,eile/ITK,rhgong/itk-with-dom,hendradarwin/ITK,hinerm/ITK,hinerm/ITK,CapeDrew/DCMTK-ITK,jcfr/ITK,fuentesdt/InsightToolkit-dev,richardbeare/ITK,thewtex/ITK,eile/ITK,thewtex/ITK,spinicist/ITK,BRAINSia/ITK,zachary-williamson/ITK,cpatrick/ITK-RemoteIO,hjmjohnson/ITK,zachary-williamson/ITK,fbudin69500/ITK,ajjl/ITK,Kitware/ITK,blowekamp/ITK,zachary-williamson/ITK,biotrump/ITK,msmolens/ITK,msmolens/ITK,blowekamp/ITK,hendradarwin/ITK,PlutoniumHeart/ITK,InsightSoftwareConsortium/ITK,hjmjohnson/ITK,vfonov/ITK,fedral/ITK,GEHC-Surgery/ITK,spinicist/ITK,LucasGandel/ITK,paulnovo/ITK,biotrump/ITK,malaterre/ITK,biotrump/ITK,hjmjohnson/ITK,PlutoniumHeart/ITK,thewtex/ITK,jcfr/ITK,fuentesdt/InsightToolkit-dev,itkvideo/ITK,richardbeare/ITK,vfonov/ITK,biotrump/ITK,fbudin69500/ITK,cpatrick/ITK-RemoteIO,cpatrick/ITK-RemoteIO,spinicist/ITK,hendradarwin/ITK,thewtex/ITK,blowekamp/ITK,msmolens/ITK,paulnovo/ITK,jmerkow/ITK,itkvideo/ITK,LucasGandel/ITK,InsightSoftwareConsortium/ITK,CapeDrew/DCMTK-ITK,BlueBrain/ITK,jmerkow/ITK,ajjl/ITK,jcfr/ITK,InsightSoftwareConsortium/ITK,atsnyder/ITK,LucasGandel/ITK,hjmjohnson/ITK,InsightSoftwareConsortium/ITK,cpatrick/ITK-RemoteIO,hinerm/ITK,spinicist/ITK,itkvideo/ITK,zachary-williamson/ITK,vfonov/ITK,richardbeare/ITK,BRAINSia/ITK,BlueBrain/ITK,LucasGandel/ITK,fuentesdt/InsightToolkit-dev,CapeDrew/DCMTK-ITK,jmerkow/ITK,GEHC-Surgery/ITK,hendradarwin/ITK,rhgong/itk-with-dom,BRAINSia/ITK,malaterre/ITK,rhgong/itk-with-dom,ajjl/ITK,eile/ITK,fbudin69500/ITK,stnava/ITK,richardbeare/ITK,vfonov/ITK,fedral/ITK,fbudin69500/ITK,richardbeare/ITK,malaterre/ITK,itkvideo/ITK,fedral/ITK,BlueBrain/ITK,BlueBrain/ITK,zachary-williamson/ITK,BRAINSia/ITK,fedral/ITK,jmerkow/ITK,malaterre/ITK,fbudin69500/ITK,blowekamp/ITK,zachary-williamson/ITK,fbudin69500/ITK,jmerkow/ITK,itkvideo/ITK,BlueBrain/ITK,hendradarwin/ITK,ajjl/ITK,hendradarwin/ITK,eile/ITK,itkvideo/ITK,rhgong/itk-with-dom,hinerm/ITK,rhgong/itk-with-dom,msmolens/ITK,heimdali/ITK,Kitware/ITK,atsnyder/ITK,InsightSoftwareConsortium/ITK,InsightSoftwareConsortium/ITK,vfonov/ITK,paulnovo/ITK,fuentesdt/InsightToolkit-dev,hinerm/ITK,thewtex/ITK,GEHC-Surgery/ITK,malaterre/ITK,msmolens/ITK,stnava/ITK,cpatrick/ITK-RemoteIO,msmolens/ITK,msmolens/ITK,CapeDrew/DCMTK-ITK,eile/ITK,ajjl/ITK,jcfr/ITK,PlutoniumHeart/ITK,fbudin69500/ITK,Kitware/ITK,jcfr/ITK,atsnyder/ITK,ajjl/ITK,zachary-williamson/ITK,LucasGandel/ITK,msmolens/ITK,paulnovo/ITK,fuentesdt/InsightToolkit-dev,vfonov/ITK,atsnyder/ITK,LucHermitte/ITK,malaterre/ITK,ajjl/ITK,GEHC-Surgery/ITK,hinerm/ITK,vfonov/ITK,ajjl/ITK,LucHermitte/ITK,rhgong/itk-with-dom,LucHermitte/ITK,paulnovo/ITK,hjmjohnson/ITK,blowekamp/ITK,atsnyder/ITK,malaterre/ITK,stnava/ITK,eile/ITK,eile/ITK,fedral/ITK,CapeDrew/DCMTK-ITK,heimdali/ITK,PlutoniumHeart/ITK,LucasGandel/ITK,paulnovo/ITK,biotrump/ITK,CapeDrew/DCMTK-ITK,thewtex/ITK,LucHermitte/ITK,cpatrick/ITK-RemoteIO,heimdali/ITK,PlutoniumHeart/ITK,richardbeare/ITK,hendradarwin/ITK,hinerm/ITK,LucHermitte/ITK,biotrump/ITK,BRAINSia/ITK,PlutoniumHeart/ITK,heimdali/ITK,biotrump/ITK,LucHermitte/ITK,stnava/ITK,jcfr/ITK,spinicist/ITK,heimdali/ITK,fedral/ITK,heimdali/ITK,LucHermitte/ITK,fuentesdt/InsightToolkit-dev,hjmjohnson/ITK,blowekamp/ITK,blowekamp/ITK,fbudin69500/ITK,itkvideo/ITK,atsnyder/ITK,PlutoniumHeart/ITK,hjmjohnson/ITK,stnava/ITK,Kitware/ITK,fuentesdt/InsightToolkit-dev,hinerm/ITK,stnava/ITK,eile/ITK,vfonov/ITK,cpatrick/ITK-RemoteIO,Kitware/ITK,BRAINSia/ITK,GEHC-Surgery/ITK,spinicist/ITK,GEHC-Surgery/ITK,LucasGandel/ITK,stnava/ITK,LucHermitte/ITK,itkvideo/ITK,jmerkow/ITK,spinicist/ITK,thewtex/ITK,spinicist/ITK,jcfr/ITK,hendradarwin/ITK,jcfr/ITK,InsightSoftwareConsortium/ITK,jmerkow/ITK,Kitware/ITK,fedral/ITK,fedral/ITK,malaterre/ITK,BlueBrain/ITK,cpatrick/ITK-RemoteIO,BRAINSia/ITK,fuentesdt/InsightToolkit-dev,CapeDrew/DCMTK-ITK,stnava/ITK,BlueBrain/ITK,heimdali/ITK,paulnovo/ITK,hinerm/ITK,CapeDrew/DCMTK-ITK,GEHC-Surgery/ITK,fuentesdt/InsightToolkit-dev