Customizing Git Merge Drivers and Attributes

the work tree, but leave the path in the conflicted state for the user to sort out. union:: Run 3-way file level merge for text files, but take lines from both versions, instead of leaving conflict markers. This tends to leave the added lines in the resulting file in random order and the user should verify the result. Do not use this if you do not understand the implications. Defining a custom merge driver ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The definition of a merge driver is done in the `.git/config` file, not in the `gitattributes` file, so strictly speaking this manual page is a wrong place to talk about it. However... To define a custom merge driver `filfre`, add a section to your `$GIT_DIR/config` file (or `$HOME/.gitconfig` file) like this: ---------------------------------------------------------------- [merge "filfre"] name = feel-free merge driver driver = filfre %O %A %B %L %P recursive = binary ---------------------------------------------------------------- The `merge.*.name` variable gives the driver a human-readable name. The `merge.*.driver` variable's value is used to construct a command to run to common ancestor's version (`%O`), current version (`%A`) and the other branches' version (`%B`). These three tokens are replaced with the names of temporary files that hold the contents of these versions when the command line is built. Additionally, `%L` will be replaced with the conflict marker size (see below). The merge driver is expected to leave the result of the merge in the file named with `%A` by overwriting it, and exit with zero status if it managed to merge them cleanly, or non-zero if there were conflicts. When the driver crashes (e.g. killed by SEGV), it is expected to exit with non-zero status that are higher than 128, and in such a case, the merge results in a failure (which is different from producing a conflict). The `merge.*.recursive` variable specifies what other merge driver to use when the merge driver is called for an internal merge between common ancestors, when there are more than one. When left unspecified, the driver itself is used for both internal merge and the final merge. The merge driver can learn the pathname in which the merged result will be stored via placeholder `%P`. The conflict labels to be used for the common ancestor, local head and other head can be passed by using `%S`, `%X` and `%Y` respectively. `conflict-marker-size` ^^^^^^^^^^^^^^^^^^^^^^ This attribute controls the length of conflict markers left in the work tree file during a conflicted merge. Only a positive integer has a meaningful effect. For example, this line in `.gitattributes` can be used to tell the merge machinery to leave much longer (instead of the usual 7-character-long) conflict markers when merging the file `Documentation/git-merge.adoc` results in a conflict. ------------------------ Documentation/git-merge.adoc conflict-marker-size=32 ------------------------ Checking whitespace errors ~~~~~~~~~~~~~~~~~~~~~~~~~~ `whitespace` ^^^^^^^^^^^^ The `core.whitespace` configuration variable allows you to define what 'diff' and 'apply' should consider whitespace errors for all paths in the project (See linkgit:git-config[1]). This attribute gives you finer control per path. Set:: Notice all types of potential whitespace errors known to Git. The tab width is taken from the value of the `core.whitespace` configuration variable. Unset:: Do not notice anything as error. Unspecified:: Use the value of the `core.whitespace` configuration variable to decide what to notice as error. String:: Specify a comma separated list of common whitespace problems to notice in the same format as the `core.whitespace` configuration variable. Creating an archive ~~~~~~~~~~~~~~~~~~~ `export-ignore` ^^^^^^^^^^^^^^^ Files and directories with the attribute `export-ignore` won't be added to archive files. `export-subst` ^^^^^^^^^^^^^^ If the attribute `export-subst` is set for a file

Git allows customization of merge drivers and attributes, including defining custom merge drivers, specifying conflict marker sizes, and controlling whitespace errors, to fine-tune the merge and diff process for specific files and projects.