Not sure if this is a Mercurial problem or problem of the NetBeans external binaries hook, so starting here.

I tried to fetch new changes from the remote repository, and the fetch ended with:
abort: /usr/local/home/lahvac/src/nb/outgoing/libs.javacimpl/external/javac-impl-nb-7.0-b07.jar looks like a binary file.

(full session is:
pulling from http://hg.netbeans.org/main
searching for changes
adding changesets
adding manifests
adding file changes
added 62 changesets with 246 changes to 241 files (+1 heads)
updating to 95548:7c70be712357
Downloading http://hg.netbeans.org/binaries/2366BE318BCA6C0434673F1382028B7B5DF357BA-javac-impl-nb-7.0-b07.jar
243 files updated, 0 files merged, 12 files removed, 0 files unresolved
merging with 95486:0145ad606dcb
merging libs.javacimpl/external/javac-impl-nb-7.0-b07.jar
abort: /usr/local/home/lahvac/src/nb/outgoing/libs.javacimpl/external/javac-impl-nb-7.0-b07.jar looks like a binary file.
)

The problem seems to be that the "libs.javacimpl/external/javac-impl-nb-7.0-b07.jar" library has been changed both
"locally" and "remotely", and the merge will fail. The log contains the change ids, so it should be possible to
reproduce the merge once I push all my changes (which will take a while now, because I am going to delete the
repository, clone a new one, do merge without the external hook, do a full build, etc.).

I saw this problem once, and the solution was to disable the external binaries hook, and do the merge over "textual"
.jar files.