[notebook] in Markdown mode, press Enter key at the end of <some http link>, the next line is indented unexpectly

[oseack]

Steps:
1.In a cell, change to markdown mode
2.enter something like http://www.google.ca, then press Enter key
3.notice the next line will be indented.

"http://www.google.ca" is a link not a tag, the next line shouldn't be indented. See attached screenshot.

[Carreau]

This is due to codemirror mode beeing htmlmixed instead of markdown I guess.

[Carreau]

Would you like to test #2973 ?

[minrk]

closed by #2979