patch for "bar" function

[pantxo diribarne]

Hello,

Yesterday I filled 2 bug reports about "bar" function baseline behaviour on savanah, with correponding patch attached: 
https://savannah.gnu.org/bugs/?37491

https://savannah.gnu.org/bugs/?37490

The two problems, even though both about baseline visibility, were unrelated so I did two patchs (from a local mercurial repository, following http://jordi.inversethought.com/blog/how-to-write-a-patch-for-octave/). 

I don't really understand how patchs work and I just wanted to know if that was the right way to work with bugs.

diff between original.m and modif1.m  -> patch1.patch
diff between modif1.m and modif2.m  -> patch2.patch

Even though the two patch apply to different and unrelated parts of the code, how could the second patch be applied without the first one ? Does hg diff make clever things when exporting the patch? At the second stage, does hg in fact export a diff between original.m and modif2.m excluding the modifications from the previous record ?

Sorry for the dummy question.

Pantxo