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I have recently encountered the need to generate a Mercurial diff of all changes up to a particular changeset which includes the first changeset of the repo. I realize this kind of stretches the definition of a diff, but this is for uploading a new project to a code review tool.

Let's assume the following changesets:

p83jdps99shjhwop8 - second feature 12:00 PM

hs7783909dnns9097 - first feature - 11:00 AM

a299sdnnas78s9923 - original app setup - 10:00 AM

If I need a "diff" of all changes that have been committed, the only way that I can seem to achieve this is with the following diff command...

diff -r 00:p83jdps99shjhwop8

In this case the first changeset in the argument param (here - 00) takes the regexp form of 0[0]+

This seems to be exactly what we need based on a few tests, but I have had trouble tracking down documentation on this scenario (maybe I just can't devise the right Google query). As a result, I am unsure if this will work universally, or if it happens to be specific to my setup or the repos I have tested by chance.

Is there a suggested way to achieve what I am trying to accomplish? If not, is what I described above documented anywhere?

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I believe hg diff -r null:tip is what you're after? (If everything you want is an ancestor of tip, of course). – alexis yesterday

2 Answers

up vote 1 down vote accepted

It appears this actually is documented, but you need to do some digging...

http://mercurial.selenic.com/wiki/ChangeSetID
http://mercurial.selenic.com/wiki/Nodeid

So the special nodeid you're referring to is the 'nullid'.

2 digits may not be adequate to identify the nullid as such (as it may be ambiguous if other hashes start with 2 zeros), so you may be better off specifying 4 0's or more.

Eg: hg diff -r 00:<hash of initial add changeset> has resulted in the abort: 00changelog.i@00: ambiguous identifier! error.

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It would prob be best just to use the long form of the nullid. – smp7d 16 hours ago
up vote 1 down vote

I'm a little confused about what you need. The diff between an empty repository and the revision tip is just the content of every file at tip-- in other words, it's the state of your project at tip. In diff format, that'll consist exclusively of + lines.

Anyway, if you want a way to refer to the initial state of the repository, the documented notation for it is null (see hg help revisions). So, to get a diff between the initial (empty) state and the state of your repository at tip, you'd just say

hg diff -r null -r tip

But hg diff gives you a diff between two points in your revision graph. So this will only give you the ancestors of tip: If there are branches (named or unnamed) that have not been merged to an ancestor of tip, you will not see them.

  3--6
 / 
0--1--2--5--7 (tip)
    \   / 
      4

In the above example, the range from null to 7 does not include revisions 3 and 6.

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Thanks. I did not know that this worked. When you run this sort of diff, diff outputs the short form of the nullid @mrokitka mentioned. Both work though. – smp7d 16 hours ago
Well, you did ask for a documented way to refer to the null revision. hg help is as canonical as it gets. – alexis 11 hours ago

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