git checkout-index [-u] [-q] [-a] [-f] [-n] [--prefix=<string>] [--stage=<number>|all] [--temp] [-z] [--stdin] [--] [<file>...]
The order of the flags used to matter, but not anymore.
Just doing git checkout-index does nothing. You probably meant git checkout-index -a. And if you want to force it, you want git checkout-index -f -a.
Intuitiveness is not the goal here. Repeatability is. The reason for the "no arguments means no work" behavior is that from scripts you are supposed to be able to do:
$ find . -name '*.h' -print0 | xargs -0 git checkout-index -f --
which will force all existing *.h files to be replaced with their cached copies. If an empty command line implied "all", then this would force-refresh everything in the index, which was not the point. But since git checkout-index accepts --stdin it would be faster to use:
$ find . -name '*.h' -print0 | git checkout-index -f -z --stdin
The -- is just a good idea when you know the rest will be filenames; it will prevent problems with a filename of, for example, -a. Using -- is probably a good policy in scripts.
A listing will be written to stdout providing the association of temporary file names to tracked path names. The listing format has two variations:
The first format is what gets used when --stage is omitted or is not --stage=all. The field tempname is the temporary file name holding the file content and path is the tracked path name in the index. Only the requested entries are output.
The second format is what gets used when --stage=all. The three stage temporary fields (stage1temp, stage2temp, stage3temp) list the name of the temporary file if there is a stage entry in the index or . if there is no stage entry. Paths which only have a stage 0 entry will always be omitted from the output.
In both formats RS (the record separator) is newline by default but will be the null byte if -z was passed on the command line. The temporary file names are always safe strings; they will never contain directory separators or whitespace characters. The path field is always relative to the current directory and the temporary file names are always relative to the top level directory.
If the object being copied out to a temporary file is a symbolic link the content of the link will be written to a normal file. It is up to the end-user or the Porcelain to make use of this information.
$ git checkout-index -n -f -a && git update-index --ignore-missing --refresh
Using git checkout-index to "export an entire tree"
$ git checkout-index --prefix=git-export-dir/ -a
git checkout-index will "export" the index into the specified directory.
The final "/" is important. The exported name is literally just prefixed with the specified string. Contrast this with the following example.
Export files with a prefix
$ git checkout-index --prefix=.merged- Makefile
This will check out the currently cached copy of Makefile into the file .merged-Makefile.