# how the commit ID come from in GIT? 3 messages from 2012-11-05 to 2012-11-05. Participants: hong zhang, Magnus Bäck, Konstantin Khomoutov. Thread: https://gitlist.dev/t/32022 ## hong zhang, 2012-11-05 20:04 Subject: how the commit ID come from in GIT? Message-ID: <1352145846.26267.YahooMailClassic@web141404.mail.bf1.yahoo.com> URL: https://gitlist.dev/e/1352145846.26267.YahooMailClassic%40web141404.mail.bf1.yahoo.com ``` List, Could anyone explain how the git commit ID will include all the files that devloper makes changes on? How git commit ID works? Thanks for any help! ---henry ``` ## Magnus Bäck, 2012-11-05 20:26 Subject: Re: how the commit ID come from in GIT? Message-ID: <20121105202621.GA31625@google.com> URL: https://gitlist.dev/e/20121105202621.GA31625%40google.com In-Reply-To: <1352145846.26267.YahooMailClassic@web141404.mail.bf1.yahoo.com> ``` On Monday, November 05, 2012 at 15:04 EST, hong zhang wrote: > Could anyone explain how the git commit ID will include all the files > that devloper makes changes on? > > How git commit ID works? In short, a Git commit points to a tree object that describes the full state of the source tree plus metadata like the commit author, date, description, and a pointer to the commit object(s) that preceded the commit. The commit id itself is the SHA-1 of the contents of the commit object. Any change of the source tree will affect the top-level tree object's SHA-1 which in turn affects the SHA-1 of the commit. Also, because a commit contains the timestamp of the commit object's creation even two commits that are content-wise identical will have different SHA-1s. If you haven't read it, the Pro Git books explains Git's object model in detail: http://git-scm.com/book/en/Git-Internals-Git-Objects That description is quite detailed, and most users don't need to go that deep. -- Magnus Bäck baeck@google.com ``` ## Konstantin Khomoutov, 2012-11-05 23:04 Subject: Re: how the commit ID come from in GIT? Message-ID: <20121105230430.GK5210@localhost.localdomain> URL: https://gitlist.dev/e/20121105230430.GK5210%40localhost.localdomain In-Reply-To: <1352145846.26267.YahooMailClassic@web141404.mail.bf1.yahoo.com> ``` On Mon, Nov 05, 2012 at 12:04:06PM -0800, hong zhang wrote: > Could anyone explain how the git commit ID will include all the files > that devloper makes changes on? > > How git commit ID works? To expand on the answer provided by Magnus, I would also suggest reading the classic "Git from the bottom up" document [1], and if you want a totally informal and fun introduction to how these cryptographic hashes come about and why they are useful, I suggest reading "The Git Parable" [2]. 1. http://newartisans.com/2008/04/git-from-the-bottom-up/ 2. http://tom.preston-werner.com/2009/05/19/the-git-parable.html ```