What does “T” mean in “git status”? (it isn’t in the man page)

It means that the type of a file changed. For example, a symbolic link that became a regular file.

As far as I know, this only applies to symlinks, submodules and regular files

Edit
A source was requested for this information. While this is simply information that’s in my head, I was able to find a few references to it on the internet. The most prominent one was a git changelog mentioning “T” as a type change and “D” as a deletion.

Edit 2 ^{(updating this because it’s my highest rating answer so far)}
As pointed out by @PhilipOakley, man git-diff-files actually does show this information.

Possible status letters are:

• A: addition of a file
• C: copy of a file into a new one
• D: deletion of a file
• M: modification of the contents or mode of a file
• R: renaming of a file
• T: change in the type of the file
• U: file is unmerged (you must complete the merge before it can be committed)
• X: “unknown” change type (most probably a bug, please report it)

As pointed out by @Mat, it’s also in diff.h, line 289:

#define DIFF_STATUS_TYPE_CHANGED    'T'

And in wt-status.c, line 282:

case DIFF_STATUS_TYPE_CHANGED:
    status_printf_more(s, c, _("typechange: %s"), one);
    break;