check if one source is consistent with another.
git vs git
In some case, one person will mirror a git repo A to A~. We need to check if A equals to A~.
tar vs tar
In some case, one person will mirror a tar A to A~. We need to check if A euqals to A~.
folder vs folder
In some case, one person will get a folder A~ from A. We need to check if A euqals to A~.
git vs tar
For example, we need to sure a git commit euqals to git release.
tar vs folder
In some case, we need to untar a tar file and use the source directly.