add some multiple pattern search in GUIDE.md

[jianhe-fun]

https://github.com/BurntSushi/ripgrep/blob/master/GUIDE.md
generally I use pipe when deal with multiple regex pattern. I know there is other way, but I don't know how to do it.
If you search in GUIDE.md, there are just so many "and" so "and" key word search is useless.
can you add some examples in GUIDE.md about multiple regex pattern. It should include key word (multiple) So people can easily search it.
reference: https://unix.stackexchange.com/questions/55359/how-to-run-grep-with-multiple-and-patterns
ps aux | rg 'postgres.*wal.*'
return

jian      148987  0.0  0.0 201184  5336 ?        Ss   Sep16   0:01 postgres: walwriter
jian      269356  0.0  0.0   8488  5916 pts/4    S+   10:27   0:00 rg postgres.*wal.*

[BurntSushi]

Your example doesn't use multiple patterns. I only see one. Can you give an actual example of what you want to see explained?

Are you talking about the -f/--file flag? Or things like rg foo | rg bar? The latter is "just" standard shell program composition.

[jianhe-fun]

Yes. rg foo | rg bar If I understand correctly, means match pattern1 foo and pattern2 bar. Obviously there is another way to express it in rg. But I don't know how.

[BurntSushi]

Why is there obviously some other way? There is not. That's what #875 is about. GNU grep doesn't have a way to do this other than grep foo | grep bar either. git grep does though.