comparison tests/test-help.t @ 39121:7c6044634957

help: describe more detail about capabilities while deciding merge tool

"hg help merge-tools" describes as below:

    (internal merge tools) will by default not handle symlinks or
    binary files.

But in some cases, Mercurial assumes that internal merge tools have
one or both of these capabilities.

"hg help merge-tools" also describes as below, for matching patterns in
merge-patterns configuration section. But this is not sufficient.

    Here, binary capabilities of the merge tool are not considered.

This patch describes more detail about capabilities while deciding
merge tool.

39120:d7007b807fa2

         must be executable by the shell.
      2. If the "HGMERGE" environment variable is present, its value is used and
         must be executable by the shell.
      3. If the filename of the file to be merged matches any of the patterns in
         the merge-patterns configuration section, the first usable merge tool
         corresponding to a matching pattern is used. Here, binary capabilities
         of the merge tool are not considered.
      4. If ui.merge is set it will be considered next. If the value is not the
         name of a configured tool, the specified value is used and must be
         executable by the shell. Otherwise the named tool is used if it is
         usable.
      5. If any usable merge tools are present in the merge-tools configuration

      6. If a program named "hgmerge" can be found on the system, it is used -
         but it will by default not be used for symlinks and binary files.
      7. If the file to be merged is not binary and is not a symlink, then
         internal ":merge" is used.
      8. Otherwise, ":prompt" is used.
  
      Note:
         After selecting a merge program, Mercurial will by default attempt to
         merge the files using a simple merge algorithm first. Only if it
         doesn't succeed because of conflicting changes will Mercurial actually

39121:7c6044634957

         must be executable by the shell.
      2. If the "HGMERGE" environment variable is present, its value is used and
         must be executable by the shell.
      3. If the filename of the file to be merged matches any of the patterns in
         the merge-patterns configuration section, the first usable merge tool
         corresponding to a matching pattern is used.
      4. If ui.merge is set it will be considered next. If the value is not the
         name of a configured tool, the specified value is used and must be
         executable by the shell. Otherwise the named tool is used if it is
         usable.
      5. If any usable merge tools are present in the merge-tools configuration

      6. If a program named "hgmerge" can be found on the system, it is used -
         but it will by default not be used for symlinks and binary files.
      7. If the file to be merged is not binary and is not a symlink, then
         internal ":merge" is used.
      8. Otherwise, ":prompt" is used.
  
      For historical reason, Mercurial assumes capabilities of internal merge
      tools as below while examining rules above, regardless of actual
      capabilities of them.
  
      step specified via  binary symlink
      ----------------------------------
      1.   --tool         o      o
      2.   HGMERGE        o      o
      3.   merge-patterns o      x
      4.   ui.merge       x      x
  
      Note:
         After selecting a merge program, Mercurial will by default attempt to
         merge the files using a simple merge algorithm first. Only if it
         doesn't succeed because of conflicting changes will Mercurial actually