branchcache: stop writing more branchcache file on disk than needed

Before this change, we were unconditionally writing a branchmap file for the
filter level passed to `update_disk`. This is actually counter productive if no
update were needed for this filter level. In many case, the branch cache for a
filter level is identical to its parent "subset" and it is better to simply
keep the subset update and reuse it every time instead of having to do identical
work for similar subset.

So we change the `update_disk` method to only write a file when that filter
level differ from its parent. This removes many cases where identical files were
written, requiring multiple boring update in the test suite.

The only notable changes is the change to `test-strip-branch-cache.t`, this
case was checking a scenario that no longer reproduce the bug as writing less
branchmap file result in less stalled cache on disk.

Strictly speaking, we could create a more convoluted scenario that create a
similar issue. However the next changeset would also cover that scenario so we
directly updated that test case to a "no longer buggy" state.

mercurial/branchmap.py

@@ -85,7 +85,8 b' class BranchMapCache:'
             bcache._filtername,
             repo.filtername,
         )
-        bcache.write(repo)
+        if bcache._dirty:
+            bcache.write(repo)
 
     def updatecache(self, repo):
         """Update the cache for the given filtered view on a repository"""

tests/test-acl.t

@@ -810,7 +810,6 b' fred is not blocked from moving bookmark'
   acl: bookmark access granted: "ef1ea85a6374b77d6da9dcda9541f498f2d17df7" on bookmark "moving-bookmark"
   bundle2-input-bundle: 7 parts total
   updating the branch cache
-  invalid branch cache (served.hidden): tip differs
   added 1 changesets with 1 changes to 1 files
   bundle2-output-bundle: "HG20", 1 parts total
   bundle2-output-part: "reply:changegroup" (advisory) (params: 0 advisory) empty payload
@@ -1797,7 +1796,6 b' No branch acls specified'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-bundle: 5 parts total
   updating the branch cache
-  invalid branch cache (served.hidden): tip differs
   added 4 changesets with 4 changes to 4 files (+1 heads)
   bundle2-output-bundle: "HG20", 1 parts total
   bundle2-output-part: "reply:changegroup" (advisory) (params: 0 advisory) empty payload
@@ -2104,7 +2102,6 b' Branch acl allow other'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-bundle: 5 parts total
   updating the branch cache
-  invalid branch cache (served.hidden): tip differs
   added 4 changesets with 4 changes to 4 files (+1 heads)
   bundle2-output-bundle: "HG20", 1 parts total
   bundle2-output-part: "reply:changegroup" (advisory) (params: 0 advisory) empty payload
@@ -2196,7 +2193,6 b' push foobar into the remote'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-bundle: 5 parts total
   updating the branch cache
-  invalid branch cache (served.hidden): tip differs
   added 4 changesets with 4 changes to 4 files (+1 heads)
   bundle2-output-bundle: "HG20", 1 parts total
   bundle2-output-part: "reply:changegroup" (advisory) (params: 0 advisory) empty payload
@@ -2360,7 +2356,6 b" User 'astro' must not be denied"
   bundle2-input-part: total payload size * (glob)
   bundle2-input-bundle: 5 parts total
   updating the branch cache
-  invalid branch cache (served.hidden): tip differs
   added 4 changesets with 4 changes to 4 files (+1 heads)
   bundle2-output-bundle: "HG20", 1 parts total
   bundle2-output-part: "reply:changegroup" (advisory) (params: 0 advisory) empty payload

tests/test-blackbox.t

@@ -127,13 +127,11 b' clone, commit, pull'
   added 1 changesets with 1 changes to 1 files
   new changesets d02f48003e62
   (run 'hg update' to get a working copy)
-  $ hg blackbox -l 6
+  $ hg blackbox -l 4
   1970-01-01 00:00:00.000 bob @6563da9dcf87b1949716e38ff3e3dfaa3198eb06 (5000)> wrote branch cache (served) with 1 labels and 2 nodes
-  1970-01-01 00:00:00.000 bob @6563da9dcf87b1949716e38ff3e3dfaa3198eb06 (5000)> updated branch cache (served.hidden) in * seconds (glob)
-  1970-01-01 00:00:00.000 bob @6563da9dcf87b1949716e38ff3e3dfaa3198eb06 (5000)> wrote branch cache (served.hidden) with 1 labels and 2 nodes
   1970-01-01 00:00:00.000 bob @6563da9dcf87b1949716e38ff3e3dfaa3198eb06 (5000)> 1 incoming changes - new heads: d02f48003e62
   1970-01-01 00:00:00.000 bob @6563da9dcf87b1949716e38ff3e3dfaa3198eb06 (5000)> pull exited 0 after * seconds (glob)
-  1970-01-01 00:00:00.000 bob @6563da9dcf87b1949716e38ff3e3dfaa3198eb06 (5000)> blackbox -l 6
+  1970-01-01 00:00:00.000 bob @6563da9dcf87b1949716e38ff3e3dfaa3198eb06 (5000)> blackbox -l 4
 
 we must not cause a failure if we cannot write to the log
 
@@ -193,8 +191,8 b' backup bundles get logged'
   $ hg blackbox -l 6
   1970-01-01 00:00:00.000 bob @73f6ee326b27d820b0472f1a825e3a50f3dc489b (5000)> strip tip
   1970-01-01 00:00:00.000 bob @6563da9dcf87b1949716e38ff3e3dfaa3198eb06 (5000)> saved backup bundle to $TESTTMP/blackboxtest2/.hg/strip-backup/73f6ee326b27-7612e004-backup.hg
-  1970-01-01 00:00:00.000 bob @6563da9dcf87b1949716e38ff3e3dfaa3198eb06 (5000)> updated branch cache (immutable) in * seconds (glob)
-  1970-01-01 00:00:00.000 bob @6563da9dcf87b1949716e38ff3e3dfaa3198eb06 (5000)> wrote branch cache (immutable) with 1 labels and 2 nodes
+  1970-01-01 00:00:00.000 bob @6563da9dcf87b1949716e38ff3e3dfaa3198eb06 (5000)> updated branch cache (base) in * seconds (glob)
+  1970-01-01 00:00:00.000 bob @6563da9dcf87b1949716e38ff3e3dfaa3198eb06 (5000)> wrote branch cache (base) with 1 labels and 2 nodes
   1970-01-01 00:00:00.000 bob @6563da9dcf87b1949716e38ff3e3dfaa3198eb06 (5000)> strip tip exited 0 after * seconds (glob)
   1970-01-01 00:00:00.000 bob @6563da9dcf87b1949716e38ff3e3dfaa3198eb06 (5000)> blackbox -l 6
 

tests/test-branches.t

@@ -1316,7 +1316,7 b' Unbundling revision should warm the serv'
   new changesets 2ab8003a1750:99ba08759bc7
   updating to branch A
   0 files updated, 0 files merged, 0 files removed, 0 files unresolved
-  $ cat branchmap-update-01/.hg/cache/branch2-served
+  $ cat branchmap-update-01/.hg/cache/branch2-base
   99ba08759bc7f6fdbe5304e83d0387f35c082479 1
   99ba08759bc7f6fdbe5304e83d0387f35c082479 o A
   $ hg -R branchmap-update-01 unbundle bundle.hg
@@ -1350,7 +1350,7 b' aborted Unbundle should not update the o'
   updating to branch A
   0 files updated, 0 files merged, 0 files removed, 0 files unresolved
 
-  $ cat branchmap-update-02/.hg/cache/branch2-served
+  $ cat branchmap-update-02/.hg/cache/branch2-base
   99ba08759bc7f6fdbe5304e83d0387f35c082479 1
   99ba08759bc7f6fdbe5304e83d0387f35c082479 o A
   $ hg -R branchmap-update-02 unbundle bundle.hg --config "hooks.pretxnclose=python:$TESTTMP/simplehook.py:hook"
@@ -1361,6 +1361,6 b' aborted Unbundle should not update the o'
   rollback completed
   abort: pretxnclose hook failed
   [40]
-  $ cat branchmap-update-02/.hg/cache/branch2-served
+  $ cat branchmap-update-02/.hg/cache/branch2-base
   99ba08759bc7f6fdbe5304e83d0387f35c082479 1
   99ba08759bc7f6fdbe5304e83d0387f35c082479 o A

tests/test-clone-stream.t

@@ -220,11 +220,7 b' changes in the process.'
 #if no-stream-legacy
   $ ls -1 clone1/.hg/cache
   branch2-base
-  branch2-immutable
   branch2-served
-  branch2-served.hidden
-  branch2-visible
-  branch2-visible-hidden
   rbc-names-v1
   rbc-revs-v1
   tags2

tests/test-clone.t

@@ -47,11 +47,7 b' Ensure branchcache got copied over:'
 
   $ ls .hg/cache
   branch2-base
-  branch2-immutable
   branch2-served
-  branch2-served.hidden
-  branch2-visible
-  branch2-visible-hidden
   rbc-names-v1
   rbc-revs-v1
   tags2
@@ -71,42 +67,34 b' No update, with debug option:'
 
 #if hardlink
   $ hg --debug clone -U . ../c --config progress.debug=true
-  linking: 1/16 files (6.25%) (no-rust !)
-  linking: 2/16 files (12.50%) (no-rust !)
-  linking: 3/16 files (18.75%) (no-rust !)
-  linking: 4/16 files (25.00%) (no-rust !)
-  linking: 5/16 files (31.25%) (no-rust !)
-  linking: 6/16 files (37.50%) (no-rust !)
-  linking: 7/16 files (43.75%) (no-rust !)
-  linking: 8/16 files (50.00%) (no-rust !)
-  linking: 9/16 files (56.25%) (no-rust !)
-  linking: 10/16 files (62.50%) (no-rust !)
-  linking: 11/16 files (68.75%) (no-rust !)
-  linking: 12/16 files (75.00%) (no-rust !)
-  linking: 13/16 files (81.25%) (no-rust !)
-  linking: 14/16 files (87.50%) (no-rust !)
-  linking: 15/16 files (93.75%) (no-rust !)
-  linking: 16/16 files (100.00%) (no-rust !)
-  linked 16 files (no-rust !)
-  linking: 1/18 files (5.56%) (rust !)
-  linking: 2/18 files (11.11%) (rust !)
-  linking: 3/18 files (16.67%) (rust !)
-  linking: 4/18 files (22.22%) (rust !)
-  linking: 5/18 files (27.78%) (rust !)
-  linking: 6/18 files (33.33%) (rust !)
-  linking: 7/18 files (38.89%) (rust !)
-  linking: 8/18 files (44.44%) (rust !)
-  linking: 9/18 files (50.00%) (rust !)
-  linking: 10/18 files (55.56%) (rust !)
-  linking: 11/18 files (61.11%) (rust !)
-  linking: 12/18 files (66.67%) (rust !)
-  linking: 13/18 files (72.22%) (rust !)
-  linking: 14/18 files (77.78%) (rust !)
-  linking: 15/18 files (83.33%) (rust !)
-  linking: 16/18 files (88.89%) (rust !)
-  linking: 17/18 files (94.44%) (rust !)
-  linking: 18/18 files (100.00%) (rust !)
-  linked 18 files (rust !)
+  linking: 1/12 files (8.33%) (no-rust !)
+  linking: 2/12 files (16.67%) (no-rust !)
+  linking: 3/12 files (25.00%) (no-rust !)
+  linking: 4/12 files (33.33%) (no-rust !)
+  linking: 5/12 files (41.67%) (no-rust !)
+  linking: 6/12 files (50.00%) (no-rust !)
+  linking: 7/12 files (58.33%) (no-rust !)
+  linking: 8/12 files (66.67%) (no-rust !)
+  linking: 9/12 files (75.00%) (no-rust !)
+  linking: 10/12 files (83.33%) (no-rust !)
+  linking: 11/12 files (91.67%) (no-rust !)
+  linking: 12/12 files (100.00%) (no-rust !)
+  linked 12 files (no-rust !)
+  linking: 1/14 files (7.14%) (rust !)
+  linking: 2/14 files (14.29%) (rust !)
+  linking: 3/14 files (21.43%) (rust !)
+  linking: 4/14 files (28.57%) (rust !)
+  linking: 5/14 files (35.71%) (rust !)
+  linking: 6/14 files (42.86%) (rust !)
+  linking: 7/14 files (50.00%) (rust !)
+  linking: 8/14 files (57.14%) (rust !)
+  linking: 9/14 files (64.29%) (rust !)
+  linking: 10/14 files (71.43%) (rust !)
+  linking: 11/14 files (78.57%) (rust !)
+  linking: 12/14 files (85.71%) (rust !)
+  linking: 13/14 files (92.86%) (rust !)
+  linking: 14/14 files (100.00%) (rust !)
+  linked 14 files (rust !)
   updating the branch cache
 #else
   $ hg --debug clone -U . ../c --config progress.debug=true
@@ -125,11 +113,7 b' Ensure branchcache got copied over:'
 
   $ ls .hg/cache
   branch2-base
-  branch2-immutable
   branch2-served
-  branch2-served.hidden
-  branch2-visible
-  branch2-visible-hidden
   rbc-names-v1
   rbc-revs-v1
   tags2

tests/test-debugcommands.t

@@ -652,12 +652,7 b' Test cache warming command'
   .hg/cache/rbc-revs-v1
   .hg/cache/rbc-names-v1
   .hg/cache/hgtagsfnodes1
-  .hg/cache/branch2-visible-hidden
-  .hg/cache/branch2-visible
-  .hg/cache/branch2-served.hidden
   .hg/cache/branch2-served
-  .hg/cache/branch2-immutable
-  .hg/cache/branch2-base
 
 Test debug::unbundle
 

tests/test-hardlinks.t

@@ -263,11 +263,7 b' r4 has hardlinks in the working dir (not'
   2 r4/.hg/00changelog.i
   [24] r4/.hg/branch (re)
   2 r4/.hg/cache/branch2-base
-  2 r4/.hg/cache/branch2-immutable
   2 r4/.hg/cache/branch2-served
-  2 r4/.hg/cache/branch2-served.hidden
-  2 r4/.hg/cache/branch2-visible
-  2 r4/.hg/cache/branch2-visible-hidden
   2 r4/.hg/cache/rbc-names-v1
   2 r4/.hg/cache/rbc-revs-v1
   2 r4/.hg/cache/tags2
@@ -320,11 +316,7 b' Update back to revision 12 in r4 should '
   2 r4/.hg/00changelog.i
   1 r4/.hg/branch
   2 r4/.hg/cache/branch2-base
-  2 r4/.hg/cache/branch2-immutable
   2 r4/.hg/cache/branch2-served
-  2 r4/.hg/cache/branch2-served.hidden
-  2 r4/.hg/cache/branch2-visible
-  2 r4/.hg/cache/branch2-visible-hidden
   2 r4/.hg/cache/rbc-names-v1
   2 r4/.hg/cache/rbc-revs-v1
   2 r4/.hg/cache/tags2

tests/test-server-view.t

@@ -36,12 +36,7 b' Check same result using `experimental.ex'
   $ hg -R test --config experimental.extra-filter-revs='not public()' debugupdatecache
   $ ls -1 test/.hg/cache/
   branch2-base%89c45d2fa07e
-  branch2-immutable%89c45d2fa07e
   branch2-served
-  branch2-served%89c45d2fa07e
-  branch2-served.hidden%89c45d2fa07e
-  branch2-visible%89c45d2fa07e
-  branch2-visible-hidden%89c45d2fa07e
   hgtagsfnodes1
   rbc-names-v1
   rbc-revs-v1

tests/test-share.t

@@ -63,11 +63,7 b' Cloning a shared repo should pick up the'
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ ls -1 ../repo2-clone/.hg/cache
   branch2-base
-  branch2-immutable
   branch2-served
-  branch2-served.hidden
-  branch2-visible
-  branch2-visible-hidden
   rbc-names-v1
   rbc-revs-v1
   tags2

tests/test-ssh.t

@@ -72,8 +72,8 b' clone bookmarks via stream'
   $ hg -R local-stream book mybook
   $ hg clone --stream ssh://user@dummy/local-stream stream2
   streaming all changes
-  16 files to transfer, * of data (glob) (no-rust !)
-  18 files to transfer, * of data (glob) (rust !)
+  12 files to transfer, * of data (glob) (no-rust !)
+  14 files to transfer, * of data (glob) (rust !)
   transferred * in * seconds (*) (glob)
   updating to branch default
   2 files updated, 0 files merged, 0 files removed, 0 files unresolved

tests/test-strip-branch-cache.t

@@ -1,3 +1,5 b''
+This test cover a bug that no longer exist.
+
 Define helpers.
 
   $ hg_log () { hg log -G -T "{rev}:{node|short}"; }
@@ -18,7 +20,10 b' Setup hg repo.'
 
   $ hg pull -q ../repo
 
-  $ cat .hg/cache/branch2-visible
+  $ ls -1 .hg/cache/branch?*
+  .hg/cache/branch2-base
+  .hg/cache/branch2-served
+  $ cat .hg/cache/branch?-served
   222ae9789a75703f9836e44de7db179cbfd420ee 2
   a3498d6e39376d2456425dd8c692367bdbf00fa2 o default
   222ae9789a75703f9836e44de7db179cbfd420ee o default
@@ -33,24 +38,38 b' Setup hg repo.'
 
   $ strip '1:'
 
-The branchmap cache is not adjusted on strip.
-Now mentions a changelog entry that has been stripped.
+After the strip the "served" cache is now identical to the "base" one, and the
+older one have been actively deleted.
 
-  $ cat .hg/cache/branch2-visible
+  $ ls -1 .hg/cache/branch?*
+  .hg/cache/branch2-base
+  .hg/cache/branch2-served
+  $ cat .hg/cache/branch?-served
   222ae9789a75703f9836e44de7db179cbfd420ee 2
   a3498d6e39376d2456425dd8c692367bdbf00fa2 o default
   222ae9789a75703f9836e44de7db179cbfd420ee o default
 
-  $ commit c
-
-Not adjusted on commit, either.
+We do a new commit and we get a new valid branchmap for the served version
 
-  $ cat .hg/cache/branch2-visible
-  222ae9789a75703f9836e44de7db179cbfd420ee 2
-  a3498d6e39376d2456425dd8c692367bdbf00fa2 o default
-  222ae9789a75703f9836e44de7db179cbfd420ee o default
+  $ commit c
+  $ ls -1 .hg/cache/branch?*
+  .hg/cache/branch2-base
+  .hg/cache/branch2-served
+  $ cat .hg/cache/branch?-served
+  a1602b357cfca067600406eb19060c7128804d72 1
+  a1602b357cfca067600406eb19060c7128804d72 o default
+
 
 On pull we end up with the same tip, and so wrongly reuse the invalid cache and crash.
 
-  $ hg pull ../repo 2>&1 | grep 'ValueError:'
-  ValueError: node a3498d6e39376d2456425dd8c692367bdbf00fa2 does not exist (known-bad-output !)
+  $ hg pull ../repo --quiet
+  $ hg heads -T '{rev} {node} {branch}\n'
+  2 222ae9789a75703f9836e44de7db179cbfd420ee default
+  1 a1602b357cfca067600406eb19060c7128804d72 default
+  $ ls -1 .hg/cache/branch?*
+  .hg/cache/branch2-base
+  .hg/cache/branch2-served
+  $ cat .hg/cache/branch?-served
+  222ae9789a75703f9836e44de7db179cbfd420ee 2
+  a1602b357cfca067600406eb19060c7128804d72 o default
+  222ae9789a75703f9836e44de7db179cbfd420ee o default

tests/test-tags.t

@@ -792,11 +792,6 b' Missing tags2* files means the cache was'
 
   $ ls tagsclient/.hg/cache
   branch2-base
-  branch2-immutable
-  branch2-served
-  branch2-served.hidden
-  branch2-visible
-  branch2-visible-hidden
   hgtagsfnodes1
   rbc-names-v1
   rbc-revs-v1
@@ -823,11 +818,6 b' Running hg tags should produce tags2* fi'
 
   $ ls tagsclient/.hg/cache
   branch2-base
-  branch2-immutable
-  branch2-served
-  branch2-served.hidden
-  branch2-visible
-  branch2-visible-hidden
   hgtagsfnodes1
   rbc-names-v1
   rbc-revs-v1

tests/test-treemanifest.t

@@ -761,8 +761,8 b' Stream clone with basicstore'
   $ hg clone --config experimental.changegroup3=True --stream -U \
   >   http://localhost:$HGPORT1 stream-clone-basicstore
   streaming all changes
-  29 files to transfer, * of data (glob) (no-rust !)
-  31 files to transfer, * of data (glob) (rust !)
+  24 files to transfer, * of data (glob) (no-rust !)
+  26 files to transfer, * of data (glob) (rust !)
   transferred * in * seconds (*) (glob)
   $ hg -R stream-clone-basicstore verify -q
   $ cat port-1-errors.log
@@ -771,8 +771,8 b' Stream clone with encodedstore'
   $ hg clone --config experimental.changegroup3=True --stream -U \
   >   http://localhost:$HGPORT2 stream-clone-encodedstore
   streaming all changes
-  29 files to transfer, * of data (glob) (no-rust !)
-  31 files to transfer, * of data (glob) (rust !)
+  24 files to transfer, * of data (glob) (no-rust !)
+  26 files to transfer, * of data (glob) (rust !)
   transferred * in * seconds (*) (glob)
   $ hg -R stream-clone-encodedstore verify -q
   $ cat port-2-errors.log