Re: git am from scratch

[Jeff King <peff@peff.net>]

On Thu, Mar 19, 2009 at 09:42:49PM +0100, Andreas Gruenbacher wrote:

> > I don't think this has ever worked in any version of git.
> I did find a way to help myself in the end. Still it was still a major, 
> unnecessary annoyance.

Sure, and that is why I suggested a patch for git-am might be welcome;
it's not the right tool for the job, but it seems to be one that people
naturally think of.

> I ran into this problem when trying to reconstruct a project's history (after 
> going RCS -> CVS -> git many things were still wrong like unrelated RCS files 
> which ended up in the history, RCS files being moved to the Attic in the 
> original tree to indicate deletes [which means they will happily live on from 
> a CVS point of view], etc.).

Yikes. Out of curiosity, what did you use to do the CVS import?


Anyway, here is a not-very-well-tested patch to get "git am" to apply on
top of an empty repository (i.e., it worked on my utterly simplistic
test case and I didn't think too hard about what else might have been
broken). Maybe it will give a good start to somebody who wants to work
on this.

---
diff --git a/git-am.sh b/git-am.sh
index d339075..bcc600d 100755
--- a/git-am.sh
+++ b/git-am.sh
@@ -290,17 +290,23 @@ else
 		: >"$dotest/rebasing"
 	else
 		: >"$dotest/applying"
-		git update-ref ORIG_HEAD HEAD
+		if git rev-parse --quiet --verify HEAD; then
+			git update-ref ORIG_HEAD HEAD
+		else
+			rm -f "$GIT_DIR/ORIG_HEAD"
+		fi
 	fi
 fi
 
 case "$resolved" in
 '')
-	files=$(git diff-index --cached --name-only HEAD --) || exit
-	if test "$files"
-	then
-		: >"$dotest/dirtyindex"
-		die "Dirty index: cannot apply patches (dirty: $files)"
+	if git rev-parse --quiet --verify HEAD; then
+		files=$(git diff-index --cached --name-only HEAD --) || exit
+		if test "$files"
+		then
+			: >"$dotest/dirtyindex"
+			die "Dirty index: cannot apply patches (dirty: $files)"
+		fi
 	fi
 esac
 
@@ -541,7 +547,7 @@ do
 	fi
 
 	tree=$(git write-tree) &&
-	parent=$(git rev-parse --verify HEAD) &&
+	parent=$(git rev-parse --quiet --verify HEAD)
 	commit=$(
 		if test -n "$ignore_date"
 		then
@@ -552,7 +558,7 @@ do
 			GIT_COMMITTER_DATE="$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