dag: Add --mermaid and --md option.

[daavoo]

• ❗ I have followed the Contributing to DVC checklist.

• 📖 If this PR requires documentation updates, I have created a separate PR (or issue, at least) in dvc.org and linked it here.

---

Now that mermaid can be embedded in github md:

dvc dag --md >> dag.md
cml send-comment dag.md

[skshetry]

🔥

[skshetry]

We could extend this with subgraphs to show individual pipelines in the future.

flowchart TD
	node1[data/data.xml.dvc]
	node2[evaluate]
	node3[featurize]
	node4[prepare]
	node5[train]
	node6[data2.dvc]

	subgraph P1
    node6
    end

    subgraph P2
	node1-->node4
	node3-->node2
	node3-->node5
	node4-->node3
	node5-->node2
    end

flowchart TD
	node1[data/data.xml.dvc]
	node2[evaluate]
	node3[featurize]
	node4[prepare]
	node5[train]
	node6[data2.dvc]

	subgraph P1
    node6
    end

    subgraph P2
	node1-->node4
	node3-->node2
	node3-->node5
	node4-->node3
	node5-->node2
    end

Loading

[daavoo]

We could extend this with subgraphs to show individual pipelines in the future.

flowchart TD
	node1[data/data.xml.dvc]
	node2[evaluate]
	node3[featurize]
	node4[prepare]
	node5[train]
	node6[data2.dvc]

	subgraph P1
    node6
    end

    subgraph P2
	node1-->node4
	node3-->node2
	node3-->node5
	node4-->node3
	node5-->node2
    end

That was a doubt I had because I couldn't find an example test.

When it's possible for get_pipelines to return more than 1 pipeline @skshetry ?

[skshetry]

This is now inconsistent with other --md flags, in that they never add ``` (backticks).

[daavoo]

This is now inconsistent with other --md flags, in that they never add ``` (backticks).

I see your point. However, the way I understand it is that --md outputs a self-contained MarkDown "component".

On the one hand, the other --md flags output a MarkDown table, because it's the component that best suits the data to be shown.

On the other, this command would generate a MarkDown codeblock, which is also a self-contained MarkDown component, because it's suitable for the data to be shown.

I see inconsistency in the fact that this is the first --md option not outputting a table, but I see consistency on all outputting self-contained MarkDown components.

[casperdcl]

Definitely prefer "self-contained markdown component with backticks"

• it's --md not (just) --mermaid. In fact --md may even imply --mermaid.
• it works well with CML reports

stale

[casperdcl]

@daavoo as @0x2b3bfa0 said, maybe --mermaid (without --md) should not have fencing.

[0x2b3bfa0]

```
🤺
```

[dberenbaum]

What's the status of this PR?

[daavoo]

@daavoo as @0x2b3bfa0 said, maybe --mermaid (without --md) should not have fencing.

This is already the current status