$ curl cheat.sh/
# meld
# Graphical diffing and merging tool.
# More information: <https://meldmerge.org/>.

# Start meld:
meld

# Compare 2 files:
meld path/to/file_1 path/to/file_2

# Compare 2 directories:
meld path/to/directory_1 path/to/directory_2

# Compare 3 files:
meld path/to/file_1 path/to/file_2 path/to/file_3

# Open a comparison as a new tab in a pre-existing meld instance:
meld --newtab path/to/file_1 path/to/file_2

# Compare multiple sets of files:
meld --diff path/to/file_1 path/to/file_2 --diff path/to/file_3 path/to/file_4

$
Follow @igor_chubin cheat.sh tldr