update for modifying files

1 files changed, 45 insertions, 20 deletions

diff --git a/doc/walkthrough.mdwn b/doc/walkthrough.mdwn
index 29922bd75..cfdf0ddab 100644
--- a/doc/walkthrough.mdwn
+++ b/doc/walkthrough.mdwn
@@ -139,6 +139,51 @@ But `other.iso` looks to have never been copied to anywhere else, so if
 it's something you want to hold onto, you'd need to transfer it to
 some other repository before dropping it.
 
+## modifying annexed files
+
+Normally, the content of files in the annex is prevented from being modified.
+
+	# echo oops > my_cool_big_file
+	bash: my_cool_big_file: Permission deined
+
+In order to modify a file, it should first be unlocked.
+
+	# git annex unlock my_cool_big_file
+	unlock my_cool_big_file (copying...) ok
+
+They replaces the symlink that normally points at its content with a copy
+of the content. You can then modify the file like any regular file. Because
+it is a regular file.
+
+If you decide you don't need to modify the file after all, or want to discard
+modifications, just use `git annex lock`.
+
+When you `git commit`, git-annex's pre-commit hook will automatically
+notice that you are committing an unlocked file, and add its new content
+to the annex. The file will be replaced with a symlink to the new content,
+and this symlink is what gets committed to git in the end.
+
+	# echo "now smaller, but even cooler" > my_cool_big_file
+	# git commit my_cool_big_file -m "changed an annexed file"
+	add my_cool_big_file ok
+	(Recording state in git...)
+	[master 64cda67] changed an annexed file
+	 2 files changed, 2 insertions(+), 1 deletions(-)
+	 create mode 100644 .git-annex/SHA1:0b1d8616d0238cb9418a0e0a649bdad2e9e7faae.log
+
+There is one problem with using `git commit` like this: Git wants to first
+stage the entire contents of the file in its index. That can be slow for
+big files (sorta why git-annex exists in the first place). So, the
+automatic handling on commit is a nice safety feature, since it prevents
+the file content being accidentially commited into git. But when working with
+big files, it's faster to explicitly add them to the annex yourself
+before committing.
+
+	# echo "now smaller, but even cooler yet" > my_cool_big_file
+	# git annex add my_cool_big_file
+	add my_cool_big_file ok
+	# git commit my_cool_big_file -m "changed an annexed file"
+
 ## using ssh remotes
 
 So far in this walkthrough, git-annex has been used with a remote
@@ -190,26 +235,6 @@ makes it very easy.
 	WORM:1274316523:86050597:hackity_hack_and_kax 100%   82MB 199.1KB/s   07:02
 	ok
 
-## modifying annexed files
-
-Normally, the content of files in the annex is prevented from being modified.
-In order to modify a file, it should first be unlocked:
-
-	# git annex unlock my_cool_big_file
-	unlock my_cool_big_file (copying...) ok
-
-They replaces the symlink that normally points at its content with a copy
-of the content. You can then modify the file like any regular file. Because
-it is a regular file.
-
-When you `git commit`, git-annex's pre-commit hook will automatically
-notice that you are committing an unlocked file, and add its new content
-to the annex. The file will be replaced with a symlink to the new content,
-and this symlink is what gets committed to git.
-
-If you decide you don't need to modify the file after all, or want to discard
-modifications, just use the lock subcommand.
-
 ## using the URL backend
 
 git-annex has multiple key-value [[backends]]. So far this walkthrough has