Set Git attributes for BAM and CRAM files in the repository

Author: jmarshall

.gitattributes

@@ -1,3 +1,11 @@
+# Ensure BAM and CRAM files are left as binary.  To display changes in them
+# by converting to SAM, add to your configuration (perhaps with --global):
+#
+#	git config diff.bam.textconv  "samtools view -h"
+#	git config diff.cram.textconv "samtools view -h"
+*.bam     -text diff=bam
+*.cram    -text diff=cram
+
 # Omit these files from release tarballs.
 .git*           export-ignore
 /.travis.yml    export-ignore