[libcxx-commits] [libcxx] [libc++] Add a merge driver that can apply clang-format (PR #73712)

[via libcxx-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libcxx

Author: Louis Dionne (ldionne)

<details>
<summary>Changes</summary>

In preparation for the moment when we'll clang-format the whole code base, this patch adds a script that can be used to rebase patches across clang-format changes mechanically, without requiring manual intervention.

See https://discourse.llvm.org/t/rfc-clang-formatting-all-of-libc-once-and-for-all.

---
Full diff: https://github.com/llvm/llvm-project/pull/73712.diff


1 Files Affected:

- (added) libcxx/utils/clang-format-merge-driver.sh (+38) 


``````````diff
diff --git a/libcxx/utils/clang-format-merge-driver.sh b/libcxx/utils/clang-format-merge-driver.sh
new file mode 100755
index 000000000000000..6b1a339720d76a4
--- /dev/null
+++ b/libcxx/utils/clang-format-merge-driver.sh
@@ -0,0 +1,38 @@
+#!/usr/bin/env bash
+
+# This script can be installed in .git/config to allow rebasing old patches across
+# libc++'s clang-format of the whole tree. Most contributors should not require that
+# since they don't have many pre-clang-format patches lying around. This script is to
+# make it easier for contributors that do have such patches.
+#
+# The script is installed by running the following from the root of your repository:
+#
+#   $ git config merge.libcxx-reformat.name "Run clang-format when rebasing libc++ patches"
+#   $ git config merge.libcxx-reformat.driver "libcxx/utils/clang-format-merge-driver.sh %O %A %B %P"
+#   $ git config merge.libcxx-reformat.recursive binary
+#
+# This is based on https://github.com/nico/hack/blob/main/notes/auto_git_rebase_across_mechanical_changes.md.
+# Many thanks to Nico Weber for paving the way here.
+
+# Path to the file's contents at the ancestor's version.
+base=$1
+
+# Path to the file's contents at the current version.
+current=$2
+
+# Path to the file's contents at the other branch's version (for nonlinear histories, there might be multiple other branches).
+other=$3
+
+# The path of the file in the repository.
+path=$4
+
+clang-format --style=file --assume-filename=$path < $base > $base.tmp
+mv $base.tmp $base
+
+clang-format --style=file --assume-filename=$path < $current > $current.tmp
+mv $current.tmp $current
+
+clang-format --style=file --assume-filename=$path < $other > $other.tmp
+mv $other.tmp $other
+
+git merge-file $current $base $other

``````````

</details>


https://github.com/llvm/llvm-project/pull/73712