Is there a Mercurial equivalent to git log --first-parent?

Question

git log --first-parent omits all but the first parent of merge commits.

Example:

$ git log --oneline --graph

* 087f5ed Master C
*   36c50a2 Merge branch 'feature'
|\  
| * 98c89df Feature B
| * 89b3a7b Feature A
* | 9a95133 Master B
|/  
* 766c9b0 Master A

$ git log --oneline --graph --first-parent

* 087f5ed Master C
* 36c50a2 Merge branch 'feature'
* 9a95133 Master B
* 766c9b0 Master A

Is there a Mercurial equivalent?

Answer 1

Direct equivalent: hg log -r '_firstancestors(...)'

There is a direct equivalent: the hidden revset _firstancestors follows the first-parent (p1) side of each merge. In Mercurial, like in Git, the first parent is the commit that was checked-out when hg merge [second parent] was called.

hg log -r '_firstancestors(myfeature)'

'hidden' means that it starts with an underscore, and is not listed in the help etc., but can still be used if you know it exists. I don't know why it is hidden.

Examples

This revset alias lists all commits on a feature branch while ignoring all the ancestry whenever master is merged into the branch to bring it up-to-date. (The shop I work prefers merging over rebasing).

[revsetalias]
feature($1) = _firstancestors($1) and not _firstancestors(master)

[alias]
f = log -r "feature($(echo $HG_ARGS| sed 's/^f //'))"

Example usage (uses my own logging template):

$ hg f myfeature
o  423 myfeature default/myfeature -- Esteis -- 2016-07-12 -- 123abc
|  this
o    422 -- Esteis -- 2016-07-12 -- 123def
|\   merge master into myfeature
o ~  421 -- Esteis -- 2016-07-12 -- 456abc
|    that
o  420 -- Esteis -- 2016-07-12 -- 789def
|  and the other

Answer 2

You can use revsets for this:

hg log -r "p1(merge())"

merge() gets all the merge commits and p1() gets the first parent of those commits.

Use hg help revsets to get more information on revsets.