merge: store commitinfo if these is a dc or cd conflict

delete-changed or changed-delete conflicts can either be resolved by mergetool,
if some tool is passed and using or by user choose something on prompt or user
doing some `hg revert` after choosing the file to remain conflicted.

If the user decides to keep the changed side, on commit we just reuse the parent
filenode. This is mostly fine unless we are in a distributed environment and
people are doing criss-cross merges.

Since, we don't have recursive merges or any other way of describing the end
result of the merge was an explicit choice and it should be differentiated from
it's ancestors, merge algo during criss-cross merges fails to take in account
the explicit choice made by user and end up with a what-can-be-said-wrong-merge.

The solution which we are trying to fix this is by creating a filenode on commit
instead of reusing the parent filenode. This helps differentiate between
pre-merged filenode and post-merge filenode and kind of tells about the choice
user made.

To implement creating new filenode functionality, we store info about these
files in mergestate so that we can read them on commit and force create a new
filenode.

Differential Revision: https://phab.mercurial-scm.org/D8988

mercurial/merge.py

@@ -909,6 +909,10 b' def manifestmerge('
                             (f, None, f, False, pa.node()),
                             b'prompt changed/deleted',
                         )
+                        if branchmerge:
+                            mresult.addcommitinfo(
+                                f, b'merge-removal-candidate', b'yes'
+                            )
                 elif n1 == addednodeid:
                     # This file was locally added. We should forget it instead of
                     # deleting it.
@@ -1018,6 +1022,10 b' def manifestmerge('
                         (None, f, f, False, pa.node()),
                         b'prompt deleted/changed',
                     )
+                    if branchmerge:
+                        mresult.addcommitinfo(
+                            f, b'merge-removal-candidate', b'yes'
+                        )
             else:
                 mresult.addfile(
                     f,

tests/test-merge-changedelete.t

@@ -83,11 +83,13 b' Non-interactive merge:'
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
     other path: file1 (node 0000000000000000000000000000000000000000)
     extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+    extra: merge-removal-candidate = yes
   file: file2 (state "u")
     local path: file2 (hash 0000000000000000000000000000000000000000, flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
     extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+    extra: merge-removal-candidate = yes
   file: file3 (state "u")
     local path: file3 (hash d5b0a58bc47161b1b8a831084b366f757c4f0b11, flags "")
     ancestor path: file3 (node 2661d26c649684b482d10f91960cc3db683c38b4)
@@ -148,11 +150,13 b' Interactive merge:'
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
     other path: file1 (node 0000000000000000000000000000000000000000)
     extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+    extra: merge-removal-candidate = yes
   file: file2 (state "r")
     local path: file2 (hash 0000000000000000000000000000000000000000, flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
     extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+    extra: merge-removal-candidate = yes
   file: file3 (state "u")
     local path: file3 (hash d5b0a58bc47161b1b8a831084b366f757c4f0b11, flags "")
     ancestor path: file3 (node 2661d26c649684b482d10f91960cc3db683c38b4)
@@ -226,11 +230,13 b' Interactive merge with bad input:'
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
     other path: file1 (node 0000000000000000000000000000000000000000)
     extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+    extra: merge-removal-candidate = yes
   file: file2 (state "r")
     local path: file2 (hash 0000000000000000000000000000000000000000, flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
     extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+    extra: merge-removal-candidate = yes
   file: file3 (state "u")
     local path: file3 (hash d5b0a58bc47161b1b8a831084b366f757c4f0b11, flags "")
     ancestor path: file3 (node 2661d26c649684b482d10f91960cc3db683c38b4)
@@ -288,11 +294,13 b' Interactive merge with not enough input:'
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
     other path: file1 (node 0000000000000000000000000000000000000000)
     extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+    extra: merge-removal-candidate = yes
   file: file2 (state "u")
     local path: file2 (hash 0000000000000000000000000000000000000000, flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
     extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+    extra: merge-removal-candidate = yes
   file: file3 (state "u")
     local path: file3 (hash d5b0a58bc47161b1b8a831084b366f757c4f0b11, flags "")
     ancestor path: file3 (node 2661d26c649684b482d10f91960cc3db683c38b4)
@@ -337,11 +345,13 b' Choose local versions of files'
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
     other path: file1 (node 0000000000000000000000000000000000000000)
     extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+    extra: merge-removal-candidate = yes
   file: file2 (state "r")
     local path: file2 (hash 0000000000000000000000000000000000000000, flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
     extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+    extra: merge-removal-candidate = yes
   file: file3 (state "r")
     local path: file3 (hash d5b0a58bc47161b1b8a831084b366f757c4f0b11, flags "")
     ancestor path: file3 (node 2661d26c649684b482d10f91960cc3db683c38b4)
@@ -382,11 +392,13 b' Choose other versions of files'
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
     other path: file1 (node 0000000000000000000000000000000000000000)
     extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+    extra: merge-removal-candidate = yes
   file: file2 (state "r")
     local path: file2 (hash 0000000000000000000000000000000000000000, flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
     extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+    extra: merge-removal-candidate = yes
   file: file3 (state "r")
     local path: file3 (hash d5b0a58bc47161b1b8a831084b366f757c4f0b11, flags "")
     ancestor path: file3 (node 2661d26c649684b482d10f91960cc3db683c38b4)
@@ -428,11 +440,13 b' Fail'
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
     other path: file1 (node 0000000000000000000000000000000000000000)
     extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+    extra: merge-removal-candidate = yes
   file: file2 (state "u")
     local path: file2 (hash 0000000000000000000000000000000000000000, flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
     extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+    extra: merge-removal-candidate = yes
   file: file3 (state "u")
     local path: file3 (hash d5b0a58bc47161b1b8a831084b366f757c4f0b11, flags "")
     ancestor path: file3 (node 2661d26c649684b482d10f91960cc3db683c38b4)
@@ -485,11 +499,13 b' Force prompts with no input (should be s'
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
     other path: file1 (node 0000000000000000000000000000000000000000)
     extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+    extra: merge-removal-candidate = yes
   file: file2 (state "u")
     local path: file2 (hash 0000000000000000000000000000000000000000, flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
     extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+    extra: merge-removal-candidate = yes
   file: file3 (state "u")
     local path: file3 (hash d5b0a58bc47161b1b8a831084b366f757c4f0b11, flags "")
     ancestor path: file3 (node 2661d26c649684b482d10f91960cc3db683c38b4)
@@ -544,11 +560,13 b' Force prompts'
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
     other path: file1 (node 0000000000000000000000000000000000000000)
     extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+    extra: merge-removal-candidate = yes
   file: file2 (state "u")
     local path: file2 (hash 0000000000000000000000000000000000000000, flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
     extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+    extra: merge-removal-candidate = yes
   file: file3 (state "u")
     local path: file3 (hash d5b0a58bc47161b1b8a831084b366f757c4f0b11, flags "")
     ancestor path: file3 (node 2661d26c649684b482d10f91960cc3db683c38b4)
@@ -600,11 +618,13 b' Choose to merge all files'
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
     other path: file1 (node 0000000000000000000000000000000000000000)
     extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+    extra: merge-removal-candidate = yes
   file: file2 (state "u")
     local path: file2 (hash 0000000000000000000000000000000000000000, flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
     extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+    extra: merge-removal-candidate = yes
   file: file3 (state "u")
     local path: file3 (hash d5b0a58bc47161b1b8a831084b366f757c4f0b11, flags "")
     ancestor path: file3 (node 2661d26c649684b482d10f91960cc3db683c38b4)

tests/test-merge-criss-cross.t

@@ -539,6 +539,7 b' Do all the merge combination (from the deleted or the update side \xc3\x97 keeping and deleting the file'
     ancestor path: the-file (node 4b69178b9bdae28b651393b46e631427a72f217a)
     other path: the-file (node 59e363a07dc876278f0e41756236f30213b6b460)
     extra: ancestorlinknode = 955800955977bd6c103836ee3e437276e940a589
+    extra: merge-removal-candidate = yes
   extra: other-file (filenode-source = other)
   $ hg ci -m "merge-deleting-the-file-from-deleted"
   $ hg manifest
@@ -561,6 +562,7 b' Do all the merge combination (from the deleted or the update side \xc3\x97 keeping and deleting the file'
     ancestor path: the-file (node 4b69178b9bdae28b651393b46e631427a72f217a)
     other path: the-file (node 0000000000000000000000000000000000000000)
     extra: ancestorlinknode = 955800955977bd6c103836ee3e437276e940a589
+    extra: merge-removal-candidate = yes
   $ hg ci -m "merge-deleting-the-file-from-updated"
   created new head
   $ hg manifest
@@ -583,6 +585,7 b' Do all the merge combination (from the deleted or the update side \xc3\x97 keeping and deleting the file'
     ancestor path: the-file (node 4b69178b9bdae28b651393b46e631427a72f217a)
     other path: the-file (node 59e363a07dc876278f0e41756236f30213b6b460)
     extra: ancestorlinknode = 955800955977bd6c103836ee3e437276e940a589
+    extra: merge-removal-candidate = yes
   extra: other-file (filenode-source = other)
   $ hg ci -m "merge-keeping-the-file-from-deleted"
   created new head
@@ -612,6 +615,7 b' in consideration.'
     ancestor path: the-file (node 4b69178b9bdae28b651393b46e631427a72f217a)
     other path: the-file (node 0000000000000000000000000000000000000000)
     extra: ancestorlinknode = 955800955977bd6c103836ee3e437276e940a589
+    extra: merge-removal-candidate = yes
   $ hg ci -m "merge-keeping-the-file-from-updated"
   created new head
   $ hg manifest