git-merge-tree.txt: add a section on potentional usage mistakes

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
pull/1293/head
Elijah Newren 3 months ago committed by Junio C Hamano
parent 7976721d17
commit 7260e87248
  1. 53
      Documentation/git-merge-tree.txt

@ -156,6 +156,59 @@ with linkgit:git-merge[1]:
* any messages that would have been printed to stdout (the
<<IM,Informational messages>>)
MISTAKES TO AVOID
-----------------
Do NOT look through the resulting toplevel tree to try to find which
files conflict; parse the <<CFI,Conflicted file info>> section instead.
Not only would parsing an entire tree be horrendously slow in large
repositories, there are numerous types of conflicts not representable by
conflict markers (modify/delete, mode conflict, binary file changed on
both sides, file/directory conflicts, various rename conflict
permutations, etc.)
Do NOT interpret an empty <<CFI,Conflicted file info>> list as a clean
merge; check the exit status. A merge can have conflicts without having
individual files conflict (there are a few types of directory rename
conflicts that fall into this category, and others might also be added
in the future).
Do NOT attempt to guess or make the user guess the conflict types from
the <<CFI,Conflicted file info>> list. The information there is
insufficient to do so. For example: Rename/rename(1to2) conflicts (both
sides renamed the same file differently) will result in three different
file having higher order stages (but each only has one higher order
stage), with no way (short of the <<IM,Informational messages>> section)
to determine which three files are related. File/directory conflicts
also result in a file with exactly one higher order stage.
Possibly-involved-in-directory-rename conflicts (when
"merge.directoryRenames" is unset or set to "conflicts") also result in
a file with exactly one higher order stage. In all cases, the
<<IM,Informational messages>> section has the necessary info, though it
is not designed to be machine parseable.
Do NOT assume that each paths from <<CFI,Conflicted file info>>, and
the logical conflicts in the <<IM,Informational messages>> have a
one-to-one mapping, nor that there is a one-to-many mapping, nor a
many-to-one mapping. Many-to-many mappings exist, meaning that each
path can have many logical conflict types in a single merge, and each
logical conflict type can affect many paths.
Do NOT assume all filenames listed in the <<IM,Informational messages>>
section had conflicts. Messages can be included for files that have no
conflicts, such as "Auto-merging <file>".
AVOID taking the OIDS from the <<CFI,Conflicted file info>> and
re-merging them to present the conflicts to the user. This will lose
information. Instead, look up the version of the file found within the
<<OIDTLT,OID of toplevel tree>> and show that instead. In particular,
the latter will have conflict markers annotated with the original
branch/commit being merged and, if renames were involved, the original
filename. While you could include the original branch/commit in the
conflict marker annotations when re-merging, the original filename is
not available from the <<CFI,Conflicted file info>> and thus you would
be losing information that might help the user resolve the conflict.
[[DEPMERGE]]
DEPRECATED DESCRIPTION
----------------------

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