user-manual: clarify language about "modifying" old commits

It's important to remember that git doesn't really allowing "editing" or
"modifying" commits, only replacing them by new commits.  Redo some of
the language to make this clearer.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

Documentation/user-manual.txt

@@ -1416,8 +1416,8 @@ 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>>.
 
-[[fixing-a-mistake-by-editing-history]]
-Fixing a mistake by editing history
+[[fixing-a-mistake-by-rewriting-history]]
+Fixing a mistake by rewriting history
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 If the problematic commit is the most recent commit, and you have not
@@ -1440,7 +1440,7 @@ Again, you should never do this to a commit that may already have
 been merged into another branch; use gitlink:git-revert[1] instead in
 that case.
 
-It is also possible to edit commits further back in the history, but
+It is also possible to replace commits further back in the history, but
 this is an advanced topic to be left for
 <<cleaning-up-history,another chapter>>.
 
@@ -1977,7 +1977,7 @@ This can happen, for example, if you:
 
 	- use `git reset --hard` to remove already-published commits, or
 	- use `git commit --amend` to replace already-published commits
-	  (as in <<fixing-a-mistake-by-editing-history>>), or
+	  (as in <<fixing-a-mistake-by-rewriting-history>>), or
 	- use `git rebase` to rebase any already-published commits (as
 	  in <<using-git-rebase>>).
 
@@ -2472,11 +2472,11 @@ return mywork to the state it had before you started the rebase:
 $ git rebase --abort
 -------------------------------------------------
 
-[[modifying-one-commit]]
-Modifying a single commit
+[[rewriting-one-commit]]
+Rewriting a single commit
 -------------------------
 
-We saw in <<fixing-a-mistake-by-editing-history>> that you can replace the
+We saw in <<fixing-a-mistake-by-rewriting-history>> that you can replace the
 most recent commit using
 
 -------------------------------------------------
@@ -2486,8 +2486,10 @@ $ git commit --amend
 which will replace the old commit by a new commit incorporating your
 changes, giving you a chance to edit the old commit message first.
 
-You can also use a combination of this and gitlink:git-rebase[1] to edit
-commits further back in your history.  First, tag the problematic commit with
+You can also use a combination of this and gitlink:git-rebase[1] to
+replace a commit further back in your history and recreate the
+intervening changes on top of it.  First, tag the problematic commit
+with
 
 -------------------------------------------------
 $ git tag bad mywork~5