unannex: Refuse to unannex when repo is too new to have a HEAD

In this case there must be staged changes in the index (if there is
anything to unannex), and the unannex code path needs to run with a clean
index.

1 files changed, 32 insertions, 0 deletions

diff --git a/doc/bugs/unannex_requires_commit_for_new_directories/comment_1_75814d6b4a59a4b7b950f9f2a27f0789._comment b/doc/bugs/unannex_requires_commit_for_new_directories/comment_1_75814d6b4a59a4b7b950f9f2a27f0789._comment
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+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 1"""
+ date="2015-02-25T17:45:50Z"
+ content="""
+Git provides ample facilities to remove any commits that you don't like
+from your repository's history. Eg, `git reset HEAD^^`
+
+This check for a clean index was added in [[!commit 7dc680415480fbbadc5dfd37f1ce72084fb1887d]]
+which made unannex not make 1 commit per file it unannexed. That was a
+massive improvement in speed and number of commits.
+
+In order for unannex to make just 1 commit at the end, instead of 1 per
+file, it has to stage its changes in the index. Since it then needs to
+commit the index at the end, we have one reason for it to require the index
+not have staged changes, since those stages changes would get included in
+the unannex commit.
+
+I suspect I had a second reason in mind when making that change.
+The unannex commit has to be run with the pre-commit hook disabled
+for complicated reasons. Involving other changes that are not unannex
+changes in that commit would thus defeat the fixups that the pre-commit
+hook normally does to such changes. This would at least prevent annexed
+symlink path fixups from happening, and it might result in whole unlocked
+files getting their full contents unexpectedly committed to git.
+
+There is no inconsistency between new and existing directories.
+The difference is between repositories with a HEAD and repositories too
+new to have one. Maybe it's a bug that unannex doesn't refuse to run
+in a repostory too new to have a HEAD, since it cannot tell if there are
+other staged changes with no HEAD to diff against.
+"""]]