git-commit-vandalism/Documentation/config/mergetool.txt
Jonathan Nieder b2a51c1b03 mergetool: do not enable hideResolved by default
When 98ea309b3f (mergetool: add hideResolved configuration,
2021-02-09) introduced the mergetool.hideResolved setting to reduce
the clutter in viewing non-conflicted sections of files in a
mergetool, it enabled it by default, explaining:

    No adverse effects were noted in a small survey of popular mergetools[1]
    so this behavior defaults to `true`.

In practice, alas, adverse effects do appear.  A few issues:

1. No indication is shown in the UI that the base, local, and remote
   versions shown have been modified by additional resolution.  This
   is inherent in the design: the idea of mergetool.hideResolved is to
   convince a mergetool that expects pristine local, base, and remote
   files to show partially resolved verisons of those files instead;
   there is no additional source of information accessible to the
   mergetool to see where the resolution has happened.

   (By contrast, a mergetool generating the partial resolution from
   conflict markers for itself would be able to hilight the resolved
   sections with a different color.)

   A user accustomed to seeing the files without partial resolution
   gets no indication that this behavior has changed when they upgrade
   Git.

2. If the computed merge did not line up the files correctly (for
   example due to repeated sections in the file), the partially
   resolved files can be misleading and do not have enough information
   to reconstruct what happened and compute the correct merge result.

3. Resolving a conflict can involve information beyond the textual
   conflict.  For example, if the local and remote versions added
   overlapping functionality in different ways, seeing the full
   unresolved versions of each alongside the base gives information
   about each side's intent that makes it possible to come up with a
   resolution that combines those two intents.  By contrast, when
   starting with partially resolved versions of those files, one can
   produce a subtly wrong resolution that includes redundant extra
   code added by one side that is not needed in the approach taken
   on the other.

All that said, a user wanting to focus on textual conflicts with
reduced clutter can still benefit from mergetool.hideResolved=true as
a way to deemphasize sections of the code that resolve cleanly without
requiring any changes to the invoked mergetool.  The caveats described
above are reduced when the user has explicitly turned this on, because
then the user is aware of them.

Flip the default to 'false'.

Reported-by: Dana Dahlstrom <dahlstrom@google.com>
Helped-by: Seth House <seth@eseth.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-03-13 15:30:29 -08:00

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mergetool.<tool>.path::
Override the path for the given tool. This is useful in case
your tool is not in the PATH.
mergetool.<tool>.cmd::
Specify the command to invoke the specified merge tool. The
specified command is evaluated in shell with the following
variables available: 'BASE' is the name of a temporary file
containing the common base of the files to be merged, if available;
'LOCAL' is the name of a temporary file containing the contents of
the file on the current branch; 'REMOTE' is the name of a temporary
file containing the contents of the file from the branch being
merged; 'MERGED' contains the name of the file to which the merge
tool should write the results of a successful merge.
mergetool.<tool>.hideResolved::
Allows the user to override the global `mergetool.hideResolved` value
for a specific tool. See `mergetool.hideResolved` for the full
description.
mergetool.<tool>.trustExitCode::
For a custom merge command, specify whether the exit code of
the merge command can be used to determine whether the merge was
successful. If this is not set to true then the merge target file
timestamp is checked and the merge assumed to have been successful
if the file has been updated, otherwise the user is prompted to
indicate the success of the merge.
mergetool.meld.hasOutput::
Older versions of `meld` do not support the `--output` option.
Git will attempt to detect whether `meld` supports `--output`
by inspecting the output of `meld --help`. Configuring
`mergetool.meld.hasOutput` will make Git skip these checks and
use the configured value instead. Setting `mergetool.meld.hasOutput`
to `true` tells Git to unconditionally use the `--output` option,
and `false` avoids using `--output`.
mergetool.meld.useAutoMerge::
When the `--auto-merge` is given, meld will merge all non-conflicting
parts automatically, highlight the conflicting parts and wait for
user decision. Setting `mergetool.meld.useAutoMerge` to `true` tells
Git to unconditionally use the `--auto-merge` option with `meld`.
Setting this value to `auto` makes git detect whether `--auto-merge`
is supported and will only use `--auto-merge` when available. A
value of `false` avoids using `--auto-merge` altogether, and is the
default value.
mergetool.hideResolved::
During a merge Git will automatically resolve as many conflicts as
possible and write the 'MERGED' file containing conflict markers around
any conflicts that it cannot resolve; 'LOCAL' and 'REMOTE' normally
represent the versions of the file from before Git's conflict
resolution. This flag causes 'LOCAL' and 'REMOTE' to be overwriten so
that only the unresolved conflicts are presented to the merge tool. Can
be configured per-tool via the `mergetool.<tool>.hideResolved`
configuration variable. Defaults to `false`.
mergetool.keepBackup::
After performing a merge, the original file with conflict markers
can be saved as a file with a `.orig` extension. If this variable
is set to `false` then this file is not preserved. Defaults to
`true` (i.e. keep the backup files).
mergetool.keepTemporaries::
When invoking a custom merge tool, Git uses a set of temporary
files to pass to the tool. If the tool returns an error and this
variable is set to `true`, then these temporary files will be
preserved, otherwise they will be removed after the tool has
exited. Defaults to `false`.
mergetool.writeToTemp::
Git writes temporary 'BASE', 'LOCAL', and 'REMOTE' versions of
conflicting files in the worktree by default. Git will attempt
to use a temporary directory for these files when set `true`.
Defaults to `false`.
mergetool.prompt::
Prompt before each invocation of the merge resolution program.