add symlink content fetching support

imgbom/scope/resolvers/test-fixtures/image-symlinks/Dockerfile

@@ -0,0 +1,24 @@
+# LAYER 0:
+FROM busybox:latest
+
+# LAYER 1:
+ADD file-1.txt .
+# LAYER 2: link with previous data
+RUN ln -s ./file-1.txt link-1
+
+# LAYER 3: link with future data
+RUN ln -s ./file-2.txt link-2
+# LAYER 4:
+ADD file-2.txt .
+
+# LAYER 5: link with current data
+RUN echo "file 3" > file-3.txt && ln -s ./file-3.txt link-within
+
+# LAYER 6: multiple links (link-indirect > link-2 > file-2.txt)
+RUN ln -s ./link-2 link-indirect
+
+# LAYER 7: override contents / resolution
+ADD new-file-2.txt file-2.txt
+
+# LAYER 8: dead link
+RUN ln -s ./i-dont-exist.txt link-dead

imgbom/scope/resolvers/test-fixtures/image-symlinks/file-1.txt

@@ -0,0 +1 @@
+file 1!

imgbom/scope/resolvers/test-fixtures/image-symlinks/file-2.txt

@@ -0,0 +1 @@
+file 2!

imgbom/scope/resolvers/test-fixtures/image-symlinks/new-file-2.txt

@@ -0,0 +1 @@
+NEW file override!