Do a "git export" (like "svn export")?
Probably the simplest way to achieve this is with git archive. If you really need just the expanded tree you can do something like this.
git archive master | tar -x -C /somewhere/else
Most of the time that I need to 'export' something from git, I want a compressed archive in any case so I do something like this.
git archive master | bzip2 >source-tree.tar.bz2
ZIP archive:
git archive --format zip --output /full/path/to/zipfile.zip master
git help archive for more details, it's quite flexible.
Be aware that even though the archive will not contain the .git directory, it will, however, contain other hidden git-specific files like .gitignore, .gitattributes, etc. If you don't want them in the archive, make sure you use the export-ignore attribute in a .gitattributes file and commit this before doing your archive. Read more...
Note: If you are interested in exporting the index, the command is
git checkout-index -a -f --prefix=/destination/path/
(See Greg's answer for more details)
I found out what option 2 means. From a repository, you can do:
git checkout-index -a -f --prefix=/destination/path/
The slash at the end of the path is important, otherwise it will result in the files being in /destination with a prefix of 'path'.
Since in a normal situation the index contains the contents of the repository, there is nothing special to do to "read the desired tree into the index". It's already there.
The -a flag is required to check out all files in the index (I'm not sure what it means to omit this flag in this situation, since it doesn't do what I want). The -f flag forces overwriting any existing files in the output, which this command doesn't normally do.
This appears to be the sort of "git export" I was looking for.