bat-test.dockerfile: make tests/source a volume

Takes out a moving part so the probability of image layer cache
invalidation (and so `bat cache --build`) decreases.

It only depends on the syntax now. And the bat version.

.dockerignore

@@ -3,4 +3,3 @@
 *
 !/syntaxes/
 !/tests/docker/*regression.sh
-!/tests/source

tests/docker/bat-test.dockerfile

@@ -12,7 +12,6 @@ COPY --from=fetch-pkg  /tmp/bat.deb  /tmp
 RUN dpkg --install /tmp/bat.deb
 ENV COLORTERM=truecolor
 COPY ./tests/docker/*regression.sh  /tests/
-COPY ./tests/source  /tests/source
 COPY ./syntaxes/cmd-help.sublime-syntax  /root/.config/bat/syntaxes/
 RUN bat cache --build > /dev/null
 ENTRYPOINT /tests/run_highlight_regression.sh

tests/highlight_regression.sh

@@ -6,8 +6,11 @@ cd "$(dirname "${BASH_SOURCE[0]}")"
 
 docker build --quiet -f docker/bat-test.dockerfile -t bat-test ..
 
-volume="$PWD"/highlighted:/tests/highlighted
-docker run -v "$volume" bat-test
+vol1="$PWD"/source:/tests/source:ro
+vol2="$PWD"/highlighted:/tests/highlighted
+docker run \
+    -v "$vol1" -v "$vol2" \
+    bat-test
 
 # have git tell the effective difference between the version of the syntax
 # in staging/HEAD and the one in working dir, for all highlighted samples

tests/theme_regression.sh

@@ -6,8 +6,10 @@ cd "$(dirname "${BASH_SOURCE[0]}")"
 
 docker build --quiet -f docker/bat-test.dockerfile -t bat-test ..
 
-volume="$PWD"/theme:/tests/theme
-docker run -v "$volume" \
+vol1="$PWD"/source:/tests/source:ro
+vol2="$PWD"/theme:/tests/theme
+docker run \
+    -v "$vol1" -v "$vol2" \
     --entrypoint /tests/run_theme_regression.sh \
     bat-test