core-tutorial: Catch up with current Git

No longer talk about Cogito since it's deprecated.  Some scripts (such as
git-reset or git-branch) have undergone builtinification so adjust the text
to reflect this.

Fix a typo in the description of git-show-branch (merges are indicated by a
`-', not by a `.').

git-pull/git-push do not seem to use the dumb git-ssh-fetch/git-ssh-upload
(the text was probably missing a word).

Adjust a link that wasn't rendered properly because it was wrapped.

Signed-off-by: Benoit Sigoure <tsuna@lrde.epita.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/core-tutorial.txt

@@ -553,13 +553,8 @@ can explore on your own.
 
 [NOTE]
 Most likely, you are not directly using the core
-git Plumbing commands, but using Porcelain like Cogito on top
-of it. Cogito works a bit differently and you usually do not
-have to run `git-update-index` yourself for changed files (you
-do tell underlying git about additions and removals via
-`cg-add` and `cg-rm` commands). Just before you make a commit
-with `cg-commit`, Cogito figures out which files you modified,
-and runs `git-update-index` on them for you.
+git Plumbing commands, but using Porcelain such as `git-add`, `git-rm'
+and `git-commit'.
 
 
 Tagging a version
@@ -686,8 +681,8 @@ $ git reset
 
 and in fact a lot of the common git command combinations can be scripted
 with the `git xyz` interfaces.  You can learn things by just looking
-at what the various git scripts do.  For example, `git reset` is the
-above two lines implemented in `git-reset`, but some things like
+at what the various git scripts do.  For example, `git reset` used to be
+the above two lines implemented in `git-reset`, but some things like
 `git status` and `git commit` are slightly more complex scripts around
 the basic git commands.
 
@@ -805,8 +800,8 @@ you have, you can say
 $ git branch
 ------------
 
-which is nothing more than a simple script around `ls .git/refs/heads`.
-There will be asterisk in front of the branch you are currently on.
+which used to be nothing more than a simple script around `ls .git/refs/heads`.
+There will be an asterisk in front of the branch you are currently on.
 
 Sometimes you may wish to create a new branch _without_ actually
 checking it out and switching to it. If so, just use the command
@@ -952,7 +947,7 @@ the later output lines is used to show commits contained in the
 `master` branch, and the second column for the `mybranch`
 branch. Three commits are shown along with their log messages.
 All of them have non blank characters in the first column (`*`
-shows an ordinary commit on the current branch, `.` is a merge commit), which
+shows an ordinary commit on the current branch, `-` is a merge commit), which
 means they are now part of the `master` branch. Only the "Some
 work" commit has the plus `+` character in the second column,
 because `mybranch` has not been merged to incorporate these
@@ -1086,7 +1081,7 @@ to help dumb transport downloaders.
 There are (confusingly enough) `git-ssh-fetch` and `git-ssh-upload`
 programs, which are 'commit walkers'; they outlived their
 usefulness when git Native and SSH transports were introduced,
-and not used by `git pull` or `git push` scripts.
+and are not used by `git pull` or `git push` scripts.
 
 Once you fetch from the remote repository, you `merge` that
 with your current branch.
@@ -1193,7 +1188,7 @@ $ mb=$(git-merge-base HEAD mybranch)
 
 The command writes the commit object name of the common ancestor
 to the standard output, so we captured its output to a variable,
-because we will be using it in the next step.  BTW, the common
+because we will be using it in the next step.  By the way, the common
 ancestor commit is the "New day." commit in this case.  You can
 tell it by:
 
@@ -1459,8 +1454,7 @@ Although git is a truly distributed system, it is often
 convenient to organize your project with an informal hierarchy
 of developers. Linux kernel development is run this way. There
 is a nice illustration (page 17, "Merges to Mainline") in
-link:http://www.xenotime.net/linux/mentor/linux-mentoring-2006.pdf
-[Randy Dunlap's presentation].
+link:http://www.xenotime.net/linux/mentor/linux-mentoring-2006.pdf[Randy Dunlap's presentation].
 
 It should be stressed that this hierarchy is purely *informal*.
 There is nothing fundamental in git that enforces the "chain of