How to add a file from a branch to another branch in Mercurial?

Question

I have two branches at my local repository: default and s1.

At default branch there is a file called def.txt, among others. The s1 branch has files named as set3.txt, set1.txt, etc. I would like to add set1.txt of s1 branch to default branch as well.

I have tried to use hg add set1.txt command when the working directory is at default branch. However, because default branch does not has the file, I cannot add it and it always gives me a error message such as "no set1.txt file found".

I do not want to use merge command because I do not want to merge all other files from s1 branch to default branch. I only want to add one file, set1.txt. I have tried hg transplant -b s1, too, but it seems not serving the same purpose.

So any idea how to work around this? My goal it to have these two branches look as below:

• default: def.txt, set1.txt etc.

• s1: set1.txt, set3.txt etc.

My machine is Red Hat Linux Workstation 6 which has Mercurial 1.7.3 and TortoiseHG 1.5.

Answer 1

You can use a trick: "revert" the file set1.txt to the branch s1. Since branches are revisions, this will work:

$ hg revert -r s1 set1.txt

Answer 2

hg revert is a cute trick. I'd be more inclined to use hg cat -r s1 set1.txt > set1.txt however, that more explicitly does what you'd expect. I don't think ultimately there's any difference between the two commands.

Intuitively, you're trying to merge a single file from one branch into your current branch. A quick google turned up this article exploring this concept in a DVCS: http://josefbetancourt.wordpress.com/2011/01/13/merge-single-file-hg/