Fix issue with DiffIndex on initial commit

[zeripath]

Unfortunately #11614 introduced a bug whereby the initial commit of a
repository could not be seen due to there being no parent commit to
create a clear diff from.

Here we create a diffstat from the difference between the parentless SHA and the SHA of the empty tree - a constant known to git. (With thanks to @L0veSunshine for informing me of this SHA)

Thanks to @a1012112796 for initial attempt to fix.

Fix #11650

Closes #11674

Signed-off-by: Andrew Thornton [email protected]

[zeripath]

As ever with this part of the codebase no good deed goes unpunished.

I've said it before and no doubt I'll say it again the compare page endpoint is fragile, convoluted and highly inefficient.

It needs a complete refactor.

[a1012112796]

please review #11674 again, Thanks

[zeripath]

make lg-tm work

[a1012112796]

Ok, I see. I thought in the wrong direction. Some nits for this change.
First, as we know, the reason is that the ParsePatch does not count the real number of files but counts the number of files to be shown, so if the file number is more than max file number, it will only return it. but if the file number is less than max file number, it won't be necessary to count again. For example,

diff --git a/services/gitdiff/gitdiff.go b/services/gitdiff/gitdiff.go
index 02aef7088..7d5e31084 100644
--- a/services/gitdiff/gitdiff.go
+++ b/services/gitdiff/gitdiff.go
@@ -711,6 +711,10 @@ func GetDiffRangeWithWhitespaceBehavior(repoPath, beforeCommitID, afterCommitID
 		return nil, fmt.Errorf("Wait: %v", err)
 	}
 
+	if !diff.IsIncomplete {
+		return diff, err
+	}
+
 	shortstatArgs := []string{beforeCommitID + "..." + afterCommitID}
 	if len(beforeCommitID) == 0 || beforeCommitID == git.EmptySHA {
 		shortstatArgs = []string{git.EmptyTreeSHA, afterCommitID}

Then, I still wonder whether it's necessary to show the real number of files if the file number is more than max file number. Maybe showing a plus sign is enough, for example 100+, if users want to know more, they can increase git.MAX_GIT_DIFF_FILES when they have a good internet connection.