[PATCH 1/2] git-filter-branch.txt: clarify ident variables usage

["Tadeusz Andrzej Kadłubowski" <yess@hell.org.pl>]

There is a rare edge case of git-filter-branch: a filter that unsets
identity variables from the environment. Link to git-commit-tree
clarifies how Git would fall back in this situation.

Signed-off-by: Tadeusz Andrzej Kadłubowski <yess@hell.org.pl>
---
 Documentation/git-filter-branch.txt | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/Documentation/git-filter-branch.txt b/Documentation/git-filter-branch.txt
index dfd12c9..e50ee2f 100644
--- a/Documentation/git-filter-branch.txt
+++ b/Documentation/git-filter-branch.txt
@@ -65,9 +65,9 @@ Prior to that, the $GIT_COMMIT environment variable will be set to contain
 the id of the commit being rewritten.  Also, GIT_AUTHOR_NAME,
 GIT_AUTHOR_EMAIL, GIT_AUTHOR_DATE, GIT_COMMITTER_NAME, GIT_COMMITTER_EMAIL,
 and GIT_COMMITTER_DATE are set according to the current commit.  The values
-of these variables after the filters have run, are used for the new commit.
-If any evaluation of <command> returns a non-zero exit status, the whole
-operation will be aborted.
+of these variables after the filters have run, are used for the new commit
+(see linkgit:git-commit-tree[1] for details).  If any evaluation of <command>
+returns a non-zero exit status, the whole operation will be aborted.
  A 'map' function is available that takes an "original sha1 id" argument
 and outputs a "rewritten sha1 id" if the commit has been already
-- 
1.7.11.7