why “git show --name-only --pretty=format:” could show only names of affected files

Question

From git documentation, git show --name-only Show only names of changed files. But with command git show --name-only , it outputs other info like commit id and and author and commit messages, etc.

And I also know --pretty=format:<format> could format the output, but why given empty <format> , the output filters out other info when only using git show --name-only ?

Edited:

With exact command git show --name-only --pretty=format: (nothing after colon), the output is exactly the lines of changed files. My question is more about why given no format it outputs such result?

Answer 1

From the "DESCRIPTION" section after executing git show --help : "For commits it shows the log message and textual diff. ..."

The --name-only flag tells it not to include the textual diffs of the changed files.

The documentation could be a bit clearer here.

Answer 2

From the OPTIONS section after executing git show --help

--pretty[=] --format= Pretty-print the contents of the commit logs in a given format, ...

See the "PRETTY FORMATS" section for some additional details for each format. ...

So, --pretty affects the formatting of the commit message, and only the commit message. And from the PRETTY FORMATS section:

format:

  The format:<string> format allows you to specify which information you want to show. It works a little bit like printf 

format...

  Eg, format:"The author of %h was %an, %ar%nThe title was >>%s<<%n" would show something like this: The author of fe6e0ee was Junio C Hamano, 23 hours ago The title was >>t4119: test autocomputing -p<n> for traditional diff input.<< 

The format option allows total control over how and what is displayed, in place of the commit message. In your case, you told it you wanted nothing displayed.

Good luck.