Tab characters must not be used as a replacement of whitespace characters

[javier-godoy]

For Java sources we have the convention that "Tab characters are not used for indentation" (from Google Java Style Guide) and recently we got #43 (which among other things requires discussing which character to use for indenting XML files).

Regardless of the file format, tab characters should not be used to replace a specific number of whitespace characters, as their appearance cannot be consistently guaranteed across different devices.

While shunning tabs entirely feels too extreme, even unconventional indentation will appear consistent as long as tabs aren’t used in place of a specific number of spaces. For example, spaces and tabs could alternate based on the Fibonacci sequence (one space, one tab, two spaces, three tabs, five spaces). I’m not saying it’s a good practice, but it’s consistent.

·⟶··1)
·⟶··⟶⟶⟶1.a)
·⟶··⟶⟶⟶·····1.a.i)
·⟶··⟶⟶⟶·····1.a.2)
·⟶··⟶⟶⟶1.b)
·⟶··2)

but not

⟶1)
····2)

Then, we could add recommendations shunning tabs for specific formats.