fast-import: Allow filemodify to set the root

v1.7.3-rc0~75^2 (Teach fast-import to import subtrees named by tree id,
2010-06-30) has a shortcoming - it doesn't allow the root to be set.
Extend this behaviour by allowing the root to be referenced as the
empty path, "".

For a command (like filter-branch --subdirectory-filter) that wants
to commit a lot of trees that already exist in the object db, writing
undeltified objects as loose files only to repack them later can
involve a significant amount of overhead.
(23% slow-down observed on Linux 2.6.35, worse on Mac OS X 10.6)

Fortunately we have fast-import (which is one of the only git commands
that will write to a pack directly) but there is not an advertised way
to tell fast-import to commit a given tree without unpacking it.

This patch changes that, by allowing

	M 040000 <tree id> ""

as a filemodify line in a commit to reset to a particular tree without
any need to parse it.  For example,

	M 040000 4b825dc642cb6eb9a060e54bf8d69288fbee4904 ""

is a synonym for the deleteall command and the fast-import equivalent of

	git read-tree 4b825dc642cb6eb9a060e54bf8d69288fbee4904

Signed-off-by: David Barr <david.barr@cordelta.com>
Commit-message-by: Jonathan Nieder <jrnieder@gmail.com>
Acked-by: Sverre Rabbelier <srabbelier@gmail.com>
Tested-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/git-fast-import.txt b/Documentation/git-fast-import.txt
index 966ba4f21337e72f7be0a5b852e76a8b12192f7f..90a46665c93106ffb7976bb0bb49aea9b9debbf7 100644 (file)
--- a/Documentation/git-fast-import.txt
+++ b/Documentation/git-fast-import.txt
@@ -524,6 +524,9 @@ start with double quote (`"`).
 If an `LF` or double quote must be encoded into `<path>` shell-style
 quoting should be used, e.g. `"path/with\n and \" in it"`.
 
+Additionally, in `040000` mode, `<path>` may also be an empty string
+(`""`) to specify the root of the tree.
+
 The value of `<path>` must be in canonical form. That is it must not:
 
 * contain an empty directory component (e.g. `foo//bar` is invalid),

diff --git a/fast-import.c b/fast-import.c
index 2317b0fe7509b957577234890135509143c0872b..8f68a892342f9fdfb968c4fbc7e17d92cca11765 100644 (file)
--- a/fast-import.c
+++ b/fast-import.c
@@ -1454,6 +1454,15 @@ static int tree_content_set(
                n = slash1 - p;
        else
                n = strlen(p);
+       if (!slash1 && !n) {
+               if (!S_ISDIR(mode))
+                       die("Root cannot be a non-directory");
+               hashcpy(root->versions[1].sha1, sha1);
+               if (root->tree)
+                       release_tree_content_recursive(root->tree);
+               root->tree = subtree;
+               return 1;
+       }
        if (!n)
                die("Empty path component found in input");
        if (!slash1 && !S_ISDIR(mode) && subtree)

diff --git a/t/t9300-fast-import.sh b/t/t9300-fast-import.sh
index 7c059204e90722db20bae1d10a0988853f852262..3c0cf0509d2cfe3afc0316ed50ea85cb0d2d14de 100755 (executable)
--- a/t/t9300-fast-import.sh
+++ b/t/t9300-fast-import.sh
@@ -874,6 +874,27 @@ test_expect_success \
         git diff-tree -C --find-copies-harder -r N4^ N4 >actual &&
         compare_diff_raw expect actual'
 
+test_expect_success \
+       'N: copy root directory by tree hash' \
+       'cat >expect <<-\EOF &&
+       :100755 000000 f1fb5da718392694d0076d677d6d0e364c79b0bc 0000000000000000000000000000000000000000 D      file3/newf
+       :100644 000000 7123f7f44e39be127c5eb701e5968176ee9d78b1 0000000000000000000000000000000000000000 D      file3/oldf
+       EOF
+        root=$(git rev-parse refs/heads/branch^0^{tree}) &&
+        cat >input <<-INPUT_END &&
+       commit refs/heads/N6
+       committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+       data <<COMMIT
+       copy root directory by tree hash
+       COMMIT
+
+       from refs/heads/branch^0
+       M 040000 $root ""
+       INPUT_END
+        git fast-import <input &&
+        git diff-tree -C --find-copies-harder -r N4 N6 >actual &&
+        compare_diff_raw expect actual'
+
 test_expect_success \
        'N: modify copied tree' \
        'cat >expect <<-\EOF &&