Can I commit only parts of my code using SVN or Mercurial?

Question

I use Tortoise SVN usuallly, but I have been looking into Mercurial since it is a distributed revision control system.

What I am looking for, in both systems, is a tool

Answer 1

Mercurial can do this with the record extension.

It'll prompt you for each file and each diff hunk. For example:

% hg record
diff --git a/prelim.tex b/prelim.tex
2 hunks, 4 lines changed
examine changes to 'prelim.tex'? [Ynsfdaq?]  
@@ -12,7 +12,7 @@
 \setmonofont[Scale=0.88]{Consolas}
 % missing from xunicode.sty
 \DeclareUTFcomposite[\UTFencname]{x00ED}{\'}{\i}
-\else
+\else foo
 \usepackage[pdftex]{graphicx}
 \fi

record this change to 'prelim.tex'? [Ynsfdaq?]  
@@ -1281,3 +1281,5 @@
 %% Local variables:
 %% mode: latex
 %% End:
+
+foo
\ No newline at end of file
record this change to 'prelim.tex'? [Ynsfdaq?]  n
Waiting for Emacs...

After the commit, the remaining diff will be left behind:

% hg di
diff --git a/prelim.tex b/prelim.tex
--- a/prelim.tex
+++ b/prelim.tex
@@ -1281,3 +1281,5 @@
 %% Local variables:
 %% mode: latex
 %% End:
+
+foo
\ No newline at end of file

Alternatively, you may find it easier to use MQ (Mercurial Queues) to separate the individual changes in your repository into patches. There is a MQ variant of record (qrecord), too.

Update: Also try the crecord extension, which provides a curses interface to hunk/line selection.