git show: formatting is changed after redirection to file

I run git show --stat 2a340b71b280d60bbc29f8d8fe00b7da5760e2bb. I get:

commit 2a340b71b280d60bbc29f8d8fe00b7da5760e2bb
Author: xxx <[email protected]>
Date:   Thu Apr 30 13:40:54 2020 +0200

    xxx

 xxx.c                                |    1 +

I run git show --stat 2a340b71b280d60bbc29f8d8fe00b7da5760e2bb > git_show.txt. I get:

$ cat git_show.txt
commit 2a340b71b280d60bbc29f8d8fe00b7da5760e2bb
Author: xxx <[email protected]>
Date:   Thu Apr 30 13:40:54 2020 +0200

    xxx

 xxx.c       |    1 +

I.e. the formatting (spacing) is different! Very unexpected.

The problem is that in the git_show.txt there are also .../xxx/xxx.c | 1 + entries with clipped filenames, which prevents to see the full filename.

Why the formatting change happens and how to preserve the formatting?

P.S. git version 2.8.0

Solution

The reason is that when you print the text to standard output, Git knows what the size of your terminal is in columns, and generates a width based on that value. When you pipe to a file, Git doesn't have your terminal attached to standard output, and therefore it defaults to 80 columns.

If you want to use a different width, you can specify it as an argument to --stat:

$ git show --stat=132 2a340b71b280d60bbc29f8d8fe00b7da5760e2bb > git_show.txt
# or, if your shell supports $COLUMNS:
$ git show --stat=$COLUMNS 2a340b71b280d60bbc29f8d8fe00b7da5760e2bb > git_show.txt

There are additional parameters you can provide; for more information, see git-diff(1). Note that these options may not be available in 2.8.0; if that's the case, then you'll need to upgrade to get support for this feature.