add ignore flag

[wings132]

i'd like to add an ignore flag. If some modules' new version has bug, i want to ignore it.

[oligot]

Nice suggestion !

2 small improvements:

• we should filter the list of modules in the discover function, so that when the ignore flag is given, the ignored modules are already taken into account in this function
• to log the ignored modules, you could use the apex/log module instead of the "fmt" module, so that it's coherent with the rest of the code

[wings132]

@oligot Hi，adding ignore in discover function is a better way ! So i change the code as you said. Please review it when you are free. Thanks !

[oligot]

Hi,

I've reviewed and merged your PR.
I've used a StringSlice instead of a string to store the ignore modules from the cli.

This can be used as follow

go-mod-upgrade --ignore color --ignore cli