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[git.git] / git-applypatch.sh

diff --git a/git-applypatch.sh b/git-applypatch.sh
index 14635d9..66fd19a 100755 (executable)
--- a/git-applypatch.sh
+++ b/git-applypatch.sh
@@ -22,6 +22,8 @@ query_apply=.dotest/.query_apply
 ## if this file exists.
 keep_subject=.dotest/.keep_subject
 
+## We do not attempt the 3-way merge fallback unless this file exists.
+fall_back_3way=.dotest/.3way
 
 MSGFILE=$1
 PATCHFILE=$2
@@ -102,10 +104,79 @@ echo Applying "'$SUBJECT'"
 echo
 
 git-apply --index "$PATCHFILE" || {
+
+       # git-apply exits with status 1 when the patch does not apply,
+       # but it die()s with other failures, most notably upon corrupt
+       # patch.  In the latter case, there is no point to try applying
+       # it to another tree and do 3-way merge.
+       test $? = 1 || exit 1
+
+       test -f "$fall_back_3way" || exit 1
+
        # Here if we know which revision the patch applies to,
        # we create a temporary working tree and index, apply the
        # patch, and attempt 3-way merge with the resulting tree.
-       exit 1
+
+       O_OBJECT=`cd "$GIT_OBJECT_DIRECTORY" && pwd`
+       rm -fr .patch-merge-*
+
+       (
+               N=10
+
+               # if the patch records the base tree...
+               sed -ne '
+                       /^diff /q
+                       /^applies-to: \([0-9a-f]*\)$/{
+                               s//\1/p
+                               q
+                       }
+               ' "$PATCHFILE"
+
+               # or hoping the patch is against our recent commits...
+               git-rev-list --max-count=$N HEAD
+
+               # or hoping the patch is against known tags...
+               git-ls-remote --tags .
+       ) |
+       while read base junk
+       do
+               # Try it if we have it as a tree.
+               git-cat-file tree "$base" >/dev/null 2>&1 || continue
+
+               rm -fr .patch-merge-tmp-* &&
+               mkdir .patch-merge-tmp-dir || break
+               (
+                       cd .patch-merge-tmp-dir &&
+                       GIT_INDEX_FILE=../.patch-merge-tmp-index &&
+                       GIT_OBJECT_DIRECTORY="$O_OBJECT" &&
+                       export GIT_INDEX_FILE GIT_OBJECT_DIRECTORY &&
+                       git-read-tree "$base" &&
+                       git-apply --index &&
+                       mv ../.patch-merge-tmp-index ../.patch-merge-index &&
+                       echo "$base" >../.patch-merge-base
+               ) <"$PATCHFILE"  2>/dev/null && break
+       done
+
+       test -f .patch-merge-index &&
+       his_tree=$(GIT_INDEX_FILE=.patch-merge-index git-write-tree) &&
+       orig_tree=$(cat .patch-merge-base) &&
+       rm -fr .patch-merge-* || exit 1
+
+       echo Falling back to patching base and 3-way merge using $orig_tree...
+
+       # This is not so wrong.  Depending on which base we picked,
+       # orig_tree may be wildly different from ours, but his_tree
+       # has the same set of wildly different changes in parts the
+       # patch did not touch, so resolve ends up cancelling them,
+       # saying that we reverted all those changes.
+
+       if git-merge-resolve $orig_tree -- HEAD $his_tree
+       then
+               echo Done.
+       else
+               echo Failed to merge in the changes.
+               exit 1
+       fi
 }
 
 if test -x "$GIT_DIR"/hooks/pre-applypatch