diff tests/test-glog-beautifygraph.t @ 42621:99ebde4fec99

commit: improve the files field of changelog for merges

Currently, the files list of merge commits repeats all the deletions
(either actual deletions, or files that got renamed) that happened
between base and p2 of the merge. If p2 is the main branch, the list
can easily be much bigger than the change being merged.

This results in various problems worth improving:
- changelog is bigger than necessary
- `hg log directory` lists many unrelated merge commits, and `hg log
  -v -r commit` frequently fills multiple screens worth of files
- it possibly slows down adjustlinkrev, by forcing it to read more
  manifests, and that function can certainly be a bottleneck
- the server side of pulls can waste a lot of time simply opening the
  filelogs for pointless files (the constant factors for opening even
  a tiny filelog is apparently pretty bad)

So stop listing such files as described in the code.  Impacted merge
commits and their descendants get a different hash than they would
have without this. This doesn't seem problematic, except for
convert. The previous commit helped with that in the hg->hg case (but
if you do svn->hg twice from scratch, hashes can still change).

The rest of the description is numbers. I don't have much to report,
because recreating the files list of existing repositories is not
easy:
- debugupgradeformat and bundle/unbundle don't recreate the list
- export/import tends to choke quickly applying patches or on
  description that contain diffs,
- merge commits from the convert extension don't have the right files
  list for reasons orthogonal to the current commit
- replaying the merge with hg update/hg merge/hg revert --all/hg
  commit can end up failing in hg revert
- I wasn't sure that using debugsetparents + debugrebuilddirstate
  would really build the right thing

I measured commit time before and after this change, in a case with no
files filtered out, several files filtered out (no difference) and 5k
files filtered out (+1% time).

Recreating the 100 more recent merges in a private repo, the
concatenated uncompressed files lists goes from 1.12MB to
0.52MB. Excluding 3 merges that are not representative, then the size
goes from 570k to 15k.
I converted part of mozilla-central, and observed file list shrinking
quite a bit too, starting at the very first merge, 733641d9feaf, going
from 550 files to 10 files (although they have relatively few merges,
so they probably wouldn't care).

Differential Revision: https://phab.mercurial-scm.org/D6613

--- a/tests/test-glog-beautifygraph.t	Sat Jul 13 23:45:32 2019 -0400
+++ b/tests/test-glog-beautifygraph.t	Tue Jul 02 12:59:58 2019 -0400
@@ -2101,7 +2101,7 @@
 
   $ hg up -q 6
   $ hg log -G --git --patch --follow-first e
-  \xe2\x97\x8d  changeset:   6:fc281d8ff18d (esc)
+  \xe2\x97\x8d  changeset:   6:9feeac35a70a (esc)
   \xe2\x94\x82\xe2\x95\xb2   tag:         tip (esc)
   \xe2\x94\x82 \xe2\x95\xa7  parent:      5:99b31f1c2782 (esc)
   \xe2\x94\x82    parent:      4:17d952250a9d (esc)
@@ -2148,7 +2148,7 @@
   $ hg log -G --template "{rev} {desc|firstline}\n"
   \xe2\x97\x8b  8 add g (esc)
   \xe2\x94\x82 (esc)
-  \xe2\x94\x82 \xe2\x97\x8b  7 Added tag foo-bar for changeset fc281d8ff18d (esc)
+  \xe2\x94\x82 \xe2\x97\x8b  7 Added tag foo-bar for changeset 9feeac35a70a (esc)
   \xe2\x94\x82\xe2\x95\xb1 (esc)
   \xe2\x97\x8b  6 merge 5 and 4 (esc)
   \xe2\x94\x82\xe2\x95\xb2 (esc)
@@ -2311,17 +2311,17 @@
   # User test
   # Date 0 0
   #      Thu Jan 01 00:00:00 1970 +0000
-  # Node ID fc281d8ff18d999ad6497b3d27390bcd695dcc73
+  # Node ID 9feeac35a70aa325519bbf3178683271113f2b8f
   # Parent  99b31f1c2782e2deb1723cef08930f70fc84b37b
   # Parent  17d952250a9d03cc3dc77b199ab60e959b9b0260
   merge 5 and 4
   
-  diff -r 99b31f1c2782 -r fc281d8ff18d dir/b
+  diff -r 99b31f1c2782 -r 9feeac35a70a dir/b
   --- a/dir/b	Thu Jan 01 00:00:00 1970 +0000
   +++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
   @@ -1,1 +0,0 @@
   -a
-  diff -r 99b31f1c2782 -r fc281d8ff18d e
+  diff -r 99b31f1c2782 -r 9feeac35a70a e
   --- a/e	Thu Jan 01 00:00:00 1970 +0000
   +++ b/e	Thu Jan 01 00:00:00 1970 +0000
   @@ -1,1 +1,1 @@
@@ -2331,24 +2331,24 @@
   # User test
   # Date 0 0
   #      Thu Jan 01 00:00:00 1970 +0000
-  # Node ID 02dbb8e276b8ab7abfd07cab50c901647e75c2dd
-  # Parent  fc281d8ff18d999ad6497b3d27390bcd695dcc73
-  Added tag foo-bar for changeset fc281d8ff18d
+  # Node ID 9febbb9c8b2e09670a2fb550cb1e4e01a2c7e9fd
+  # Parent  9feeac35a70aa325519bbf3178683271113f2b8f
+  Added tag foo-bar for changeset 9feeac35a70a
   
-  diff -r fc281d8ff18d -r 02dbb8e276b8 .hgtags
+  diff -r 9feeac35a70a -r 9febbb9c8b2e .hgtags
   --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
   +++ b/.hgtags	Thu Jan 01 00:00:00 1970 +0000
   @@ -0,0 +1,1 @@
-  +fc281d8ff18d999ad6497b3d27390bcd695dcc73 foo-bar
+  +9feeac35a70aa325519bbf3178683271113f2b8f foo-bar
   # HG changeset patch
   # User test
   # Date 0 0
   #      Thu Jan 01 00:00:00 1970 +0000
-  # Node ID 24c2e826ddebf80f9dcd60b856bdb8e6715c5449
-  # Parent  fc281d8ff18d999ad6497b3d27390bcd695dcc73
+  # Node ID 3bd4551ec3fe1c0696241f236abe857a53c6d6e7
+  # Parent  9feeac35a70aa325519bbf3178683271113f2b8f
   add g
   
-  diff -r fc281d8ff18d -r 24c2e826ddeb g
+  diff -r 9feeac35a70a -r 3bd4551ec3fe g
   --- a/g	Thu Jan 01 00:00:00 1970 +0000
   +++ b/g	Thu Jan 01 00:00:00 1970 +0000
   @@ -1,2 +1,1 @@
@@ -2436,7 +2436,7 @@
   []
   <spanset- 0:9>
   $ hg log -G --template '{rev} {desc}\n'
-  \xe2\x97\x8b  7 Added tag foo-bar for changeset fc281d8ff18d (esc)
+  \xe2\x97\x8b  7 Added tag foo-bar for changeset 9feeac35a70a (esc)
   \xe2\x94\x82 (esc)
   \xe2\x97\x8b  6 merge 5 and 4 (esc)
   \xe2\x94\x82\xe2\x95\xb2 (esc)
@@ -2534,9 +2534,9 @@
 node template with changesetprinter:
 
   $ hg log -Gqr 5:7 --config ui.graphnodetemplate='"{rev}"'
-  7  7:02dbb8e276b8
+  7  7:9febbb9c8b2e
   \xe2\x94\x82 (esc)
-  6    6:fc281d8ff18d
+  6    6:9feeac35a70a
   \xe2\x94\x82\xe2\x95\xb2 (esc)
   \xe2\x94\x82 \xe2\x95\xa7 (esc)
   5  5:99b31f1c2782
@@ -2560,7 +2560,7 @@
 
   $ hg log -Gqr 7 --config extensions.color= --color=debug \
   > --config ui.graphnodetemplate='{label("branch.{branch}", rev)}'
-  [branch.default\xe2\x94\x827]  [log.node|7:02dbb8e276b8] (esc)
+  [branch.default\xe2\x94\x827]  [log.node|7:9febbb9c8b2e] (esc)
   \xe2\x94\x82 (esc)
   \xe2\x95\xa7 (esc)