DVC: add page including sub-commands destroy, diff and fetch

pages/common/dvc-diff.md

@@ -0,0 +1,24 @@
+# dvc diff
+
+> Show changes in DVC tracked file and directories added/deleted/modified
+> More information: <https://dvc.org/doc/command-reference/diff>.
+
+- Compare DVC tracked file from different Git commit/tag/branch w.r.t current workspace:
+
+`dvc diff {{commit_hash/tag/branch}}`
+
+- Compare DVC tracked file in Git b_rev w.r.t a_rev:
+
+`dvc diff b_rev a_rev`
+
+- Compare DVC tracked file, along with their latest hash:
+
+`dvc diff --show-hash {{commit}}`
+
+- Compare DVC tracked file, get output in JSON format:
+
+`dvc diff --show-json --show-hash {{commit}}`
+
+- Compare DVC tracked file, get output in Markdown format:
+
+`dvc diff --show-md --show-hash {{commit}}`