Make sure that the internal merge tools (internal:fail, internal:local, internal:union and internal:other) are used when matched by a merge-pattern in hgrc Make sure HGMERGE doesn't interfere with the test: $ unset HGMERGE $ hg init Initial file contents: $ echo "line 1" > f $ echo "line 2" >> f $ echo "line 3" >> f $ hg ci -Am "revision 0" adding f $ cat f line 1 line 2 line 3 Branch 1: editing line 1: $ sed 's/line 1/first line/' f > f.new $ mv f.new f $ hg ci -Am "edited first line" Branch 2: editing line 3: $ hg update 0 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ sed 's/line 3/third line/' f > f.new $ mv f.new f $ hg ci -Am "edited third line" created new head Merge using internal:fail tool: $ echo "[merge-patterns]" > .hg/hgrc $ echo "* = internal:fail" >> .hg/hgrc $ hg merge 0 files updated, 0 files merged, 0 files removed, 1 files unresolved use 'hg resolve' to retry unresolved file merges or 'hg update -C .' to abandon [1] $ cat f line 1 line 2 third line $ hg stat M f Merge using internal:local tool: $ hg update -C 2 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ sed 's/internal:fail/internal:local/' .hg/hgrc > .hg/hgrc.new $ mv .hg/hgrc.new .hg/hgrc $ hg merge 0 files updated, 1 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ cat f line 1 line 2 third line $ hg stat M f Merge using internal:other tool: $ hg update -C 2 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ sed 's/internal:local/internal:other/' .hg/hgrc > .hg/hgrc.new $ mv .hg/hgrc.new .hg/hgrc $ hg merge 0 files updated, 1 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ cat f first line line 2 line 3 $ hg stat M f Merge using default tool: $ hg update -C 2 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ rm .hg/hgrc $ hg merge merging f 0 files updated, 1 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ cat f first line line 2 third line $ hg stat M f Merge using internal:union tool: $ hg update -C 2 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ echo "line 4a" >>f $ hg ci -Am "Adding fourth line (commit 4)" $ hg update 2 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ echo "line 4b" >>f $ hg ci -Am "Adding fourth line v2 (commit 5)" created new head $ echo "[merge-patterns]" > .hg/hgrc $ echo "* = internal:union" >> .hg/hgrc $ hg merge 3 merging f 1 files updated, 0 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ cat f line 1 line 2 third line line 4b line 4a