[phobos] [dmd-internals] svn-->git migration

[Jason Evans]

On 01/23/2011 06:57 PM, Andrei Alexandrescu wrote:
> Say I have a change to make to one file in phobos 2 to get
> started. Could you please summarize what steps I need to take?

Let's suppose we want to update the README.txt in druntime, which 
currently refers to dsource.org.  First we need a git repository to work 
in.  Take a look at the following web page to get the appropriate ssh 
location.

   https://github.com/D-Programming-Language/druntime

Clone the repository.

   $ git clone git at github.com:D-Programming-Language/druntime.git
   $ cd druntime

Create a working branch, based on the master branch.  (I won't get much 
into branch management in this email.)

   $ git checkout -b update-README
   Switched to a new branch 'update-README'

Edit README.txt, then verify the diff.

   $ git diff
   diff --git a/README.txt b/README.txt
   index d0ae645..9183765 100644
   --- a/README.txt
   +++ b/README.txt
   @@ -1,5 +1,5 @@
    The source code repository for Druntime is:
   -http://dsource.org/projects/druntime
   +https://github.com/D-Programming-Language/druntime

    Druntime is the minimum library required to support the D programming
    language. It includes the system code required to support the garbage

Add README.txt to the staging index.

   $ git status
   # On branch update-README
   # Changed but not updated:
   #   (use "git add <file>..." to update what will be committed)
   #   (use "git checkout -- <file>..." to discard changes in working 
directory)
   #
   #       modified:   README.txt
   #
   no changes added to commit (use "git add" and/or "git commit -a")
   $ git add README.txt
   $ git diff
   $ git status
   # On branch update-README
   # Changes to be committed:
   #   (use "git reset HEAD <file>..." to unstage)
   #
   #       modified:   README.txt
   #

Commit to working branch.

   $ git commit -m "Update URL."
   [update-README 1fbddd4] Update URL.
    1 files changed, 1 insertions(+), 1 deletions(-)

Check out master branch and merge.  (If someone else had committed to 
master in the meanwhile, we would want to do a dance to "rebase" our 
working branch, but let's ignore that for now.)

   $ git checkout master
   Switched to branch 'master'
   $ git merge update-README
   Updating 559df80..1fbddd4
   Fast-forward
    README.txt |    2 +-
    1 files changed, 1 insertions(+), 1 deletions(-)

Now let's push the change to the master repository, and finally delete 
our working branch.

   $ git push origin master
   Counting objects: 5, done.
   Delta compression using up to 2 threads.
   Compressing objects: 100% (3/3), done.
   Writing objects: 100% (3/3), 330 bytes, done.
   Total 3 (delta 2), reused 0 (delta 0)
   To git at github.com:D-Programming-Language/druntime.git
      559df80..1fbddd4  master -> master
   $ git branch -d update-README
   Deleted branch update-README (was 1fbddd4).

The above example has several steps in it that can be skipped for such a 
simple change, but for more involved changes, this work flow is the 
foundation.  git is a complex tool, but the underlying concepts are 
coherent, consistent, and straightforward.  Learn those concepts well 
and you will be largely able to infer what git is capable of.

Thanks,
Jason