what is the meaning and difference PVCS version - SVN revision - GIT sha value

Question

Can any one help me to know about the difference and the meaning about PVCS version number - Subversion revision number - git sha value.

Answer 1

Subversion's revision number is the number of the commit in the repository's chronology. There is nothing magic about it. A newly created svn repository is at revision 0.
Each new commit increases the revision number and gets the new number assigned to it as its revision. The branches does not matter on this process. On Subversion, the revision number of a file is the most recent commit/revision number when the file was modified.

---

Due to its nature and internal working git cannot assign sequential numbers to commits. git uses sha1 checksums to identify anything: commits, tags, trees, blobs, files, directories. The sha1 value is computed using the content of the object it identifies.
There is no relationship between the sha1 values of related objects but changing the content of an object generates a cascading change of the sha1 that identifies the objects that depend on it. For example, if you use git rebase to move some commits from one branch to another, the sha1 identifiers of all the moved commits change.

---

I don't know anything about PVCS. Sorry.

Answer 2

PVCS and SVN are centraliazed repos:

• PVCS use a incremental number per file
• SVN use an incremental number per revision

Git is decentralized, which means it cannot use a number incremented (or it would be incremented concurrently in several distributed cloned repo)

The SHA1 represents the content of a commit (see "Git Internals - Git Objects" and "How is git commit sha1 formed ")