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basically finished up the branching section

This commit is contained in:
Scott Chacon 2010-06-04 16:37:58 +02:00
parent 4c00709b2b
commit 8195eb02e1
2 changed files with 95 additions and 2 deletions

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@ -61,7 +61,6 @@
<li><a href="/branching/#branch">checkout</a></li>
<li><a href="/branching/#merge">merge</a></li>
<li><a href="/branching/#log">log</a></li>
<li><a href="/branching/#reset">reset</a></li>
</ul>
</div>

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@ -585,6 +585,100 @@ b7ae93b added from ruby
master branch, then see how the <code>log</code> command can help us figure
out what is happening on each.</p>
<p>First we'll create a new branch to add the Erlang programming language
Hello World example - we want to do this in a branch so that we don't
muddy up our stable branch with code that may not work for a while so we
can cleanly switch in and out of it.</p>
<pre>
<b>$ git checkout -b erlang</b>
Switched to a new branch 'erlang'
<b>$ vim erlang_hw.erl</b>
<b>$ git add erlang_hw.erl </b>
<b>$ git commit -m 'added erlang'</b>
[erlang ab5ab4c] added erlang
1 files changed, 5 insertions(+), 0 deletions(-)
create mode 100644 erlang_hw.erl
</pre>
<p>Since we're having fun playing in functional programming languages we
get caught up in it and also add a Haskell example program while still in
the branch named 'erlang'.</p>
<pre>
<b>$ vim haskell.hs</b>
<b>$ git add haskell.hs </b>
<b>$ git commit -m 'added haskell'</b>
[erlang 1834130] added haskell
1 files changed, 4 insertions(+), 0 deletions(-)
create mode 100644 haskell.hs
</pre>
<p>Finally, we decide that we want to change the class name of our Ruby
program back to the way it was. So, we can go back to the master branch
and change that and we decide to just commit it directly in the master
branch instead of creating another branch.</p>
<pre>
<b>$ git checkout master</b>
Switched to branch 'master'
<b>$ ls</b>
README ruby.rb
<b>$ vim ruby.rb </b>
<b>$ git commit -am 'reverted to old class name'</b>
[master 594f90b] reverted to old class name
1 files changed, 2 insertions(+), 2 deletions(-)
</pre>
<p>So, now say we don't work on the project for a while, we have other
things to do. When we come back we want to know what the 'erlang' branch
is all about and where we've left off on the master branch. Just by looking
at the branch name, we can't know that we made Haskell changes in there, but
using <code>git log</code> we easily can. If you give Git a branch name,
it will show you just the commits that are "reachable" in the history of
that branch, that is the commits that influenced the final snapshot.</p>
<pre>
<b>$ git log --oneline erlang</b>
<span class="hl">1834130 added haskell</span>
ab5ab4c added erlang
8d585ea Merge branch 'fix_readme'
3cbb6aa fixed readme title differently
3ac015d fixed readme title
558151a Merge branch 'change_class'
b7ae93b added from ruby
3467b0a changed the class name
17f4acf first commit
</pre>
<p>This way, it's pretty easy to see that we have Haskell code included in
the branch (as I've highlighted). What is even cooler is that we can
easily tell Git that we only are interested in the commits that are
reachable in one branch that are not reachable in another, in other words
which commits are unique to a branch in comparison to another.
</p>
<p>
In this case if we are interested in merging in the 'erlang' branch we
want to see what commits are going to effect our snapshot when we do
that merge. The way we tell Git that is by putting a <code>^</code> in
front of the branch that we don't want to see. For instance, if we want
to see the commits that are in the 'erlang' branch that are not in the
'master' branch, we can do <code>erlang ^master</code>, or vice versa.
</p>
<pre>
<b>$ git log --oneline erlang ^master</b>
1834130 added haskell
ab5ab4c added erlang
<b>$ git log --oneline master ^erlang</b>
594f90b reverted to old class name
</pre>
<p>This gives us a nice, simple branch management tool. It allows us to
easily see what commits are unique to which branches so we know what
we're missing and what we would be merging in if we were to do a merge.
</p>
<p class="nutshell">
<b>In a nutshell</b> you use <code>git log</code> to list out the commit