Final

Systems in Rust

Due 09 Dec @ 5 PM PT

A Simple SCM

Realistically, consult the slides, but…

Your SCM should support minimally:

• Commit
  • Which must subsume:
    • git init
    • git add <file>
    • git commit -m <message>
• Revert
  • Which must subsume:
    • git checkout

It may optionally support:

• Viewer
  • Akin to:
    • git log
    • git diff
• Scrape
  • Akin to:
    • git reset

You are not required to implement integrity or confidentiality checks, but are encouraged to do so.

• Integrity:
  • Cache SHA2 checksums of all commits.
  • Store checksums in a Merkle tree
• Confidentiality:
  • Sign all commits using Ed25519 to encrypt the hash of the commit with a private key.
    • Likely in .ssh/id_ed25519
  • Verify signatures using the corresponding public key.

In each case you should only allow an scm revert if the integrity and/or confidentiality checks pass (depending on which you implement).

Demo

On PATH

For the sakes of this demonstration, after creating a binary - which in my case was named scm - I added it to “path” variable PATH which allows using it directly from terminal.

For example, say beginning in my home directory I made a a new crate named scm then used cargo build release to create the binary.

export PATH=~/scm/target/release/:$PATH

Read more on Stack Overflow.

Demo

A perfect final (100/100) will be able to do the following.

$ vi file.txt
$ cat file.txt
#000001 line
#000002 line
#FF0000 line
#0000FF line

$ scm commit
$ vi file.txt
$ cat file.txt
One line
Two line
Red line
Blu line

$ scm commit
$ scm revert
$ cat file.txt
#000001 line
#000002 line
#FF0000 line
#0000FF line

In brief:

• Create some version of a file which we term version \(v\)
• scm commit
• Issue some changes to the file, to a version we term version \(v'\)
• scm commit
• scm revert
• Verify that the version of the file is now restored to the earlier, version \(v\)