/etc/solr/conf/lang/hyphenations_ga.txt is in solr-common 3.6.2+dfsg-10+deb9u2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 | # Set of Irish hyphenations for StopFilter
# TODO: load this as a resource from the analyzer and sync it in build.xml
h
n
t
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