tsort(1): Add EXAMPLES section

[fernape]

Summary

Add some examples for this tool. Be aware that I did not add any examples for
-l since I can not grasp how it really works. For example, imagine a file like
this:

A B
B C
C A
A D
D E
E F
F A

This is what we show without -l:

tsort: cycle in data
tsort: A
tsort: D
tsort: E
tsort: F
F
tsort: cycle in data
tsort: A
tsort: B
tsort: C
C
A
D
B
E

and with -l:

tsort: cycle in data
tsort: A
tsort: D
tsort: E
tsort: F
F
tsort: cycle in data
tsort: A
tsort: B
tsort: C
C
A
D
B
E

So exactly the same output

Compare this with the output of OpenBSD 6.7 for the same file.

Without -l:

tsort: cycle in data
tsort: A
tsort: D
tsort: E
tsort: F
A
B
C
D
E
F

and with -l:

tsort: cycle in data
tsort: D
tsort: E
tsort: F
tsort: A
F
tsort: cycle in data
tsort: B
tsort: C
tsort: A
A
B
C
D
E

I also asked in @hackers but got no answer.

Test Plan

• mandoc -Tlint clean
• igor clean (spurious warnings about repeating letters in the examples)
• aspell happy
• man ./colrm.1 renders the page properly

[gbe]

I can't speak for the differences of the OpenBSD version of tsort, but in generell the examples are fine.

[fernape]

Thanks for reviewing!