git-am: teach git-am to apply a patch to an unborn branch

People sometimes wonder why they cannot apply a patch that only
creates new files to an unborn branch.

Signed-off-by: Nanako Shiraishi <nanako3@lavabit.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/git-am.sh b/git-am.sh
index d3390755fc687a611e89320a7bbfb4ead512c863..774383fb6893776fcd9454b080b7a8346e6b034d 100755 (executable)
--- a/git-am.sh
+++ b/git-am.sh
@@ -36,6 +36,13 @@ cd_to_toplevel
 git var GIT_COMMITTER_IDENT >/dev/null ||
        die "You need to set your committer info first"
 
+if git rev-parse --verify -q HEAD >/dev/null
+then
+       HAS_HEAD=yes
+else
+       HAS_HEAD=
+fi
+
 sq () {
        for sqarg
        do
@@ -290,16 +297,26 @@ else
                : >"$dotest/rebasing"
        else
                : >"$dotest/applying"
-               git update-ref ORIG_HEAD HEAD
+               if test -n "$HAS_HEAD"
+               then
+                       git update-ref ORIG_HEAD HEAD
+               else
+                       git update-ref -d ORIG_HEAD >/dev/null 2>&1
+               fi
        fi
 fi
 
 case "$resolved" in
 '')
-       files=$(git diff-index --cached --name-only HEAD --) || exit
+       case "$HAS_HEAD" in
+       '')
+               files=$(git ls-files) ;;
+       ?*)
+               files=$(git diff-index --cached --name-only HEAD --) ;;
+       esac || exit
        if test "$files"
        then
-               : >"$dotest/dirtyindex"
+               test -n "$HAS_HEAD" && : >"$dotest/dirtyindex"
                die "Dirty index: cannot apply patches (dirty: $files)"
        fi
 esac
@@ -541,18 +558,20 @@ do
        fi
 
        tree=$(git write-tree) &&
-       parent=$(git rev-parse --verify HEAD) &&
        commit=$(
                if test -n "$ignore_date"
                then
                        GIT_AUTHOR_DATE=
                fi
+               parent=$(git rev-parse --verify -q HEAD) ||
+               echo >&2 "applying to an empty history"
+
                if test -n "$committer_date_is_author_date"
                then
                        GIT_COMMITTER_DATE="$GIT_AUTHOR_DATE"
                        export GIT_COMMITTER_DATE
                fi &&
-               git commit-tree $tree -p $parent <"$dotest/final-commit"
+               git commit-tree $tree ${parent:+-p $parent} <"$dotest/final-commit"
        ) &&
        git update-ref -m "$GIT_REFLOG_ACTION: $FIRSTLINE" HEAD $commit $parent ||
        stop_here $this

diff --git a/t/t4150-am.sh b/t/t4150-am.sh
index 5e65afa0c10d02e50c79b550a3c142d8ff1f0674..d6ebbaebe2c258a4694cfb709809e13d24084231 100755 (executable)
--- a/t/t4150-am.sh
+++ b/t/t4150-am.sh
@@ -290,4 +290,19 @@ test_expect_success 'am --ignore-date' '
        echo "$at" | grep "+0000"
 '
 
+test_expect_success 'am into an unborn branch' '
+       rm -fr subdir &&
+       mkdir -p subdir &&
+       git format-patch --numbered-files -o subdir -1 first &&
+       (
+               cd subdir &&
+               git init &&
+               git am 1
+       ) &&
+       result=$(
+               cd subdir && git rev-parse HEAD^{tree}
+       ) &&
+       test "z$result" = "z$(git rev-parse first^{tree})"
+'
+
 test_done