refs: add "ostree refs --create" and unit tests

Added the ability to create a ref (much like a git tag) for an
existing commit through "ostree refs EXISTING --create=NEWREF".
Previously the only way to create a new ref was by creating a new commit,
but refs --create allows multiple refs to point to the same commit.

The command will fail if:
 - None/more than one existing ref is specified
 - The specified EXISTING tag does not exist, or was not specified
 - The specified NEWREF already exists, or is the name of a folder

Add unit tests in tests-ref.sh to verify above functionality

Closes: #340
Approved by: jlebon

tests/test-refs.sh

@@ -65,4 +65,35 @@ ${CMD_PREFIX} ostree refs --repo=repo | wc -l > refscount.delete3
 assert_file_has_content refscount.delete3 "^3$"
 assert_not_file_has_content reflist '^test-1$'
 
+#Add a few more commits, to test --create
+${CMD_PREFIX} ostree --repo=repo commit --branch=ctest -m ctest -s ctest tree
+${CMD_PREFIX} ostree --repo=repo commit --branch=foo/ctest -m ctest -s ctest tree
+
+${CMD_PREFIX} ostree --repo=repo refs | wc -l > refscount
+assert_file_has_content refscount "^5$"
+
+if ${CMD_PREFIX} ostree --repo=repo refs --create=ctest-new; then
+    assert_not_reached "refs --create unexpectedly succeeded without specifying an existing ref!"
+fi
+if ${CMD_PREFIX} ostree --repo=repo refs ctest --create; then
+    assert_not_reached "refs --create unexpectedly succeeded without specifying the ref to create!"
+fi
+if ${CMD_PREFIX} ostree --repo=repo refs does-not-exist --create=ctest-new; then
+    assert_not_reached "refs --create unexpectedly succeeded for a prefix that doesn't exist!"
+fi
+if ${CMD_PREFIX} ostree --repo=repo refs ctest --create=foo; then
+    assert_not_reached "refs --create unexpectedly succeeded for a prefix that is already in use by a folder!"
+fi
+if ${CMD_PREFIX} ostree --repo=repo refs foo/ctest --create=ctest; then
+    assert_not_reached "refs --create unexpectedly succeeded in overwriting an existing prefix!"
+fi
+
+#Check to see if any uncleaned tmp files were created after failed --create
+${CMD_PREFIX} ostree --repo=repo refs | wc -l > refscount.create1
+assert_file_has_content refscount.create1 "^5$"
+
+${CMD_PREFIX} ostree --repo=repo refs ctest --create ctest-new
+${CMD_PREFIX} ostree --repo=repo refs | wc -l > refscount.create2
+assert_file_has_content refscount.create2 "^6$"
+
 echo "ok refs"