Concatenating multiple changesets into one changeset

(See also [:EditingHistory])

Suppose you have a [:Repository:repository] with a number of [:ChangeSet:changesets] which you want to combine into a single changeset.

This can be done as follows using only the basic operations of Mercurial, namely [:Clone:clone], [:Push:push], and [:Pull:pull].

For simplicity, let us assume that the repository in question has a single [:Head:head], and you want to combine the last k [:Revision:revisions] into a single revision.

For concreteness, let us call the base revision R, and the ending revision R+k.

Let us furthermore assume the repository has no [:LocalModifications:local modifications].

The strategy is to take advantage of Mercurial's support for repositories with more than one head. What we do is create a [:Branch:branch] whose root revision is R and which consists of just one changeset (actually it can be multiple changesets, the principle is the same, but for simplicity let us assume one).

Diagramatically, this looks like:

Include(/fig1)

Include(/fig2)

Include(/fig3)

[:/fig1:fig 1]

[:/fig2:fig 2]

[:/fig2:fig 3]

The procedure is as follows.

  1. hg update R

    • This [:Update:updates] the [:WorkingDirectory:working directory] to revision R. Specifically, this means that the contents of the working directory are changed to that of revision R, and that R becomes the [:Parent:parent] of the working directory.

  2. hg revert -r tip --all

    • This [:Revert:reverts] the working directory to its contents at [:Tip:tip]. Since the parent of the working directory is still R, this means that the combined contents of all changesets between R and R+k show up as the modifications in the working directory.

  3. hg ci -m "Combined changesets between R and R+k"

    • At this point, [:Commit:committing] these modifications will create a changeset containing all combined changesets between revisions R and R+k.

  4. hg clone -r tip oldrepo newrepo

    • This assumes you want to get rid of your individual changesets (which are a dangling branch in oldrepo) and just keep the combined changeset (see also [:PruningDeadBranches]). newrepo will now just have the combined changeset.

CategoryTipsAndTricks