Vincent Ladeuil wrote:

quoted text
> Ok, so git make a distinction between the commit (code created by
> someone) and the tree (code only).
> 
> Commits are defined by their parents.
> 
> Trees are defined by their content only ?

Trees are collections of tuples: (mode, type, sha1, name), where mode
is simplified mode of a file or directory (only if it is symlink, directory,
file or executable file is tracked), type is blob (file) or tree
(directory), sha1 is sha1 of contents of given entry, and name is filename
of given entry.
 
quoted text
> If that's the case, how do you proceed ? 
> 
> Calculate a sha1 representing the content (or the content of the
> diff from parent) of all the files and dirs in the tree ?