[PATCH 2 of 2] rebase: skip resolved but emptied revisions

[Matt Mackall]

On Fri, 2012-04-20 at 15:08 +0200, Patrick Mezard wrote:
> # HG changeset patch
> # User Patrick Mezard <patrick at mezard.eu>
> # Date 1334927278 -7200
> # Branch stable
> # Node ID 22428bd2b8b0691f7fd4dd23d18a5b09d9da7d7a
> # Parent  39181f76286e8b6313f35da84ecd5799941ab55b
> rebase: skip resolved but emptied revisions
> 
> When rebasing, if a conflict occurs and is resolved in a way the rebased
> revision becomes empty, it is not skipped, unlike revisions being emptied
> without conflicts.
> 
> The reason is:
> - File 'x' is merged and resolved, merge.update() marks it as 'm' in the
>   dirstate.
> - rebase.concludenode() calls localrepo.commit(), which calls
>   localrepo.status() which calls dirstate.status(). 'x' shows up as 'm' and is
>   unconditionnally added to the modified files list, instead of being checked
>   again.
> - localrepo.commit() detects 'x' as changed an create a new revision where only
>   the manifest parents and linkrev differ.
> 
> Marking 'x' as modified without checking it makes sense for regular merges. But
> in rebase case, the merge looks normal but the second parent is usually
> discarded. When this happens, 'm' files in dirstate are a bit irrelevant and
> should be considered 'n' possibly dirty instead. That is what the current patch
> does.
> 
> Another approach, maybe more efficient, would be to pass another flag to
> merge.update() saying the 'branchmerge' is a bit of a lie and recordupdate()
> should call dirstate.normallookup() instead of merge().
> 
> It is also tempting to add this logic to dirstate.setparent(), moving from two
> to one parent is what invalidates the 'm' markers. But this is a far bigger
> change to make.

This probably applies to graft too, which means we want to find
somewhere to put this in core? Perhaps _filecommit() should sort this
out? Or perhaps dirstate.setparents..

> diff --git a/hgext/rebase.py b/hgext/rebase.py
> --- a/hgext/rebase.py
> +++ b/hgext/rebase.py
> @@ -362,6 +362,14 @@
>      'Commit the changes and store useful information in extra'
>      try:
>          repo.dirstate.setparents(repo[p1].node(), repo[p2].node())
> +        if p2 == nullrev:
> +            # Rebased revision has only one parent, discard merged
> +            # files 'merged' flag from dirstate to force a recheck in
> +            # status().
> +            ds = repo.dirstate
> +            for f in ds:
> +                if ds[f] == 'm':
> +                    ds.normallookup(f)
>          ctx = repo[rev]
>          if commitmsg is None:
>              commitmsg = ctx.description()
> diff --git a/tests/test-rebase-detach.t b/tests/test-rebase-detach.t
> --- a/tests/test-rebase-detach.t
> +++ b/tests/test-rebase-detach.t
> @@ -380,9 +380,7 @@
>    $ hg rebase -c
>    saved backup bundle to $TESTTMP/a7/.hg/strip-backup/6215fafa5447-backup.hg (glob)
>    $ hg  log -G --template "{rev}:{phase} '{desc}' {branches}\n"
> -  @  8:secret 'H2'
> -  |
> -  o  7:draft 'H'
> +  @  7:draft 'H'
>    |
>    | o  6:draft 'G'
>    |/|
> @@ -398,11 +396,3 @@
>    |/
>    o  0:draft 'A'
>    
> -  $ hg export 8
> -  # HG changeset patch
> -  # User test
> -  # Date 0 0
> -  # Node ID 248209b40064fe67181915fa7a4f3395520f700a
> -  # Parent  02de42196ebee42ef284b6780a87cdc96e8eaab6
> -  H2
> -  
> diff --git a/tests/test-rebase-mq-skip.t b/tests/test-rebase-mq-skip.t
> --- a/tests/test-rebase-mq-skip.t
> +++ b/tests/test-rebase-mq-skip.t
> @@ -117,9 +117,7 @@
>    saved backup bundle to $TESTTMP/b/.hg/strip-backup/*-backup.hg (glob)
>  
>    $ hg tglog
> -  @  9: 'r5' tags: 5.diff qtip tip
> -  |
> -  o  8: 'r4' tags: 4.diff
> +  @  8: 'r5' tags: 5.diff qtip tip
>    |
>    o  7: 'r2' tags: 2.diff qbase
>    |
> @@ -137,11 +135,3 @@
>    |
>    o  0: 'r0' tags:
>    
> -  $ hg export 4.diff
> -  # HG changeset patch
> -  # User test
> -  # Date 0 0
> -  # Node ID 315eb21a13c2b06e787f5d0000e36f8f8f3a1768
> -  # Parent  1660ab13ce9aea3da22ea54926bd49aeff8a4e20
> -  r4
> -  
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-- 
Mathematics is the supreme nostalgia of our time.