Add .git-blame-ignore-revs and some instructions for clang-format

3 files changed, 29 insertions, 0 deletions

diff --git a/.git-blame-ignore-revs b/.git-blame-ignore-revs
new file mode 100644
index 00000000..15c2001c
--- /dev/null
+++ b/.git-blame-ignore-revs
@@ -0,0 +1,2 @@
+# _clang_format added
+814fbda28cc8a37fed3134c2db8da28f86fb5ee0
diff --git a/README.contributors b/README.contributors
index b23f964f..65cb95a0 100644
--- a/README.contributors
+++ b/README.contributors
@@ -18,4 +18,21 @@ Poppler has three main channels of contact:
  * The #poppler channel at the IRC freenode network
 Do not hesitate to drop by talk to people there.
 
+clang-format
+------------
+We introduced clang-format mandatory usage in July 2020.
+If you want git blame to ignore the revision in which we did the mass change you can do
+   git config blame.ignoreRevsFile .git-blame-ignore-revs
+on your clone
+
+To get the clang-format warnings locally instead at CI time we recommend you
+to copy the hooks/pre-commit to your .git
+    cp hooks/pre-commit .git/hooks/
+
+We are using clang-format 10 on CI. Unfortunately clang-format is not totally
+compatible with older versions of itself. If CI gives you trouble but your local
+clang-format disagrees, just apply the changes suggested by CI and then commit
+with the --no-verify flag. If you get stuck, don't hesitate to ask the reviewer
+to help and they will reformat your commits :)
+
 And keep hacking on poppler!
diff --git a/hooks/pre-commit b/hooks/pre-commit
new file mode 100755
index 00000000..6337bbbd
--- /dev/null
+++ b/hooks/pre-commit
@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+
+readonly output=$(git clang-format -v --diff)
+
+if [[ "$output" == *"no modified files to format"* ]]; then exit 0; fi
+if [[ "$output" == *"clang-format did not modify any files"* ]]; then exit 0; fi
+
+echo "ERROR: you need to run git clang-format on your commit"
+echo "       git clang-format -f is potentially what you want"
+exit 1