Update cheatsheets

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+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# diff
+
+> Compare files and directories.
+> More information: <https://man7.org/linux/man-pages/man1/diff.1.html>.
+
+- Compare files (lists changes to turn `old_file` into `new_file`):
+
+`diff {{old_file}} {{new_file}}`
+
+- Compare files, ignoring white spaces:
+
+`diff --ignore-all-space {{old_file}} {{new_file}}`
+
+- Compare files, showing the differences side by side:
+
+`diff --side-by-side {{old_file}} {{new_file}}`
+
+- Compare files, showing the differences in unified format (as used by `git diff`):
+
+`diff --unified {{old_file}} {{new_file}}`
+
+- Compare directories recursively (shows names for differing files/directories as well as changes made to files):
+
+`diff --recursive {{old_directory}} {{new_directory}}`
+
+- Compare directories, only showing the names of files that differ:
+
+`diff --recursive --brief {{old_directory}} {{new_directory}}`
+
+- Create a patch file for Git from the differences of two text files, treating nonexistent files as empty:
+
+`diff --text --unified --new-file {{old_file}} {{new_file}} > {{diff.patch}}`