Hi,
On Tue, 6 Oct 2020, Tom Clarkson via GitGitGadget wrote:
> From: Tom Clarkson <tom@xxxxxxxxxxxxxx>
>
> Prevent a mainline commit without $dir being treated as a subtree
> commit and pulling in the entire mainline history. Any valid subtree
> commit will have only valid subtree commits as parents, which will be
> unchanged by check_parents.
I feel like this is only half the picture because I have a hard time
stitching these two sentences together.
After studying the code and your patch a bit, it appears to me that
`process_split_commit()` calls `check_parents()` first, which will call
`process_split_commit()` for all as yet unmapped parents. So basically, it
recurses until it found a commit all of whose parents are already mapped,
then permeates that information all the way back.
Doesn't this cause serious issues with stack overflows and all for long
commit histories?
> Signed-off-by: Tom Clarkson <tom@xxxxxxxxxxxxxx>
> ---
> contrib/subtree/git-subtree.sh | 24 +++++++++++-------------
> 1 file changed, 11 insertions(+), 13 deletions(-)
>
> diff --git a/contrib/subtree/git-subtree.sh b/contrib/subtree/git-subtree.sh
> index e56621a986..fa6293b372 100755
> --- a/contrib/subtree/git-subtree.sh
> +++ b/contrib/subtree/git-subtree.sh
> @@ -224,8 +224,6 @@ cache_setup () {
> fi
> mkdir -p "$cachedir" ||
> die "Can't create new cachedir: $cachedir"
> - mkdir -p "$cachedir/notree" ||
> - die "Can't create new cachedir: $cachedir/notree"
It might make sense to talk about this a bit in the commit message.
Essentially, you are replacing the `notree/<rev>` files by mapping `<rev>`
to the empty string.
This makes me wonder, again, whether the file system layout of the cache
can hold up to the demands. If a main project were to merge a subtree
with, say, 10 million commits, wouldn't that mean that `git subtree` would
now fill one directory with 10 million files? I cannot imagine that this
performs well, still.
> debug "Using cachedir: $cachedir" >&2
> }
>
> @@ -255,18 +253,11 @@ check_parents () {
> local indent=$(($2 + 1))
> for miss in $missed
> do
> - if ! test -r "$cachedir/notree/$miss"
> - then
> - debug " unprocessed parent commit: $miss ($indent)"
> - process_split_commit "$miss" "" "$indent"
> - fi
> + debug " unprocessed parent commit: $miss ($indent)"
> + process_split_commit "$miss" "" "$indent"
That makes sense to me, as the `missed` variable only contains as yet
unmapped commits, therefore we do not have to have an equivalent `test -r`
check.
Ciao,
Dscho
> done
> }
>
> -set_notree () {
> - echo "1" > "$cachedir/notree/$1"
> -}
> -
> cache_set () {
> oldrev="$1"
> newrev="$2"
> @@ -719,11 +710,18 @@ process_split_commit () {
> # vs. a mainline commit? Does it matter?
> if test -z "$tree"
> then
> - set_notree "$rev"
> if test -n "$newparents"
> then
> - cache_set "$rev" "$rev"
> + if test "$newparents" = "$parents"
> + then
> + # if all parents were subtrees, this can be a subtree commit
> + cache_set "$rev" "$rev"
> + else
> + # a mainline commit with tree missing is equivalent to the initial commit
> + cache_set "$rev" ""
> + fi
> else
> + # no parents with valid subtree mappings means a commit prior to subtree add
> cache_set "$rev" ""
> fi
> return
> --
> gitgitgadget
>
>
