When upgrading, only report changes

[lofidevops]

• Pip version: 9.0.1
• Python version: 3.5.4
• Operating system: Debian / PureOS

Description:

pip install -U -r requirements.txt

If there are no updates, I expect to see no output (or a message "No updates found.")

If there are updates, I expect to see just those updates.

If I'm feeling OCD, I expect to set a flag that shows me output for each package whether there is an update or not.

What I've run:

As above. If there are no updates, I still get output for every package. This makes it difficult to quickly see if there are updates, and which packages were updated.

[pradyunsg]

Hi @kwill!

While I don't think this change all on it's own is completely justified, this would probably be something that I'll keep in mind when discussion on completely revisiting pip install's output (#4649) resumes. :)