Additional text for undoing mistakes.

sit · sit · commit 7b593b5c19c6 · 2008-08-17T15:11:57.000-04:00
Talk about git-checkout and mention git-rebase -i.
Re-organize section to give more top-down clarity.
diff --git a/text/21_Redoing_Git_Reset_and_Revert/0_ Redoing_Git_Reset_and_Revert.markdown b/text/21_Redoing_Git_Reset_and_Revert/0_ Redoing_Git_Reset_and_Revert.markdown
@@ -1,11 +1,37 @@
-## Undoing in Git - Reset and Revert ##
+## Undoing in Git - Reset, Checkout and Revert ##
+
+Git provides multiple methods for fixing up mistakes as you
+are developing.  Selecting an appropriate method depends on whether
+or not you have committed the mistake, and if you have committed the
+mistake, whether you have shared the erroneous commit with anyone else.
+
+### Fixing un-committed mistakes ###
 
 If you've messed up the working tree, but haven't yet committed your
 mistake, you can return the entire working tree to the last committed
 state with
 
     $ git reset --hard HEAD
 
+This will throw away any changes you may have added to the git index
+and as well as any outstanding changes you have in your working tree.
+In other words, it causes the results of "git diff" and "git diff --cached"
+to both be empty.
+
+If you just want to restore just one file, say your hello.rb, use
+linkgit:git-checkout[1] instead
+
+    $ git checkout -- hello.rb
+    $ git checkout HEAD hello.rb
+
+The first command restores hello.rb to the version in the index,
+so that "git diff hello.rb" returns no differences.  The second command
+will restore hello.rb to the version in the HEAD revision, so
+that both "git diff hello.rb" and "git diff --cached hello.rb"
+return no differences.
+
+### Fixing committed mistakes ###
+
 If you make a commit that you later wish you hadn't, there are two
 fundamentally different ways to fix the problem:
 
@@ -19,8 +45,7 @@ fundamentally different ways to fix the problem:
     change, and cannot correctly perform repeated merges from
     a branch that has had its history changed.
 
-
-### Fixing a mistake with a new commit ###
+#### Fixing a mistake with a new commit ####
 
 Creating a new commit that reverts an earlier change is very easy;
 just pass the linkgit:git-revert[1] command a reference to the bad
@@ -39,4 +64,20 @@ In this case git will attempt to undo the old change while leaving
 intact any changes made since then.  If more recent changes overlap
 with the changes to be reverted, then you will be asked to fix
 conflicts manually, just as in the case of <<resolving-a-merge,
-resolving a merge>>.
+resolving a merge>>.
+
+#### Fixing a mistake by modifying a commit ####
+
+If you have just committed something but realize you need to fix
+up that commit, recent versions of linkgit:git-commit[1] support an 
+**--amend** flag which instructs git to replace the HEAD commit
+with a new one, based on the current contents of the index.  This
+gives you an opportunity to add files that you forgot to add or
+correct typos in a commit message, prior to pushing the change
+out for the world to see.
+
+If you find a mistake in an older commit, but still one that you
+have not yet published to the world, you use linkgit:git-rebase[1]
+in interactive mode, with "git rebase -i" marking the change
+that requires correction with **edit**.  This will allow you
+to amend the commit during the rebasing process.
