doc: fix asciidoc markup issues in several files

* fix incorrect use of backticks for markup in
  git-checkout.adoc, git-worktree.adoc
* switch tabs to spaces	in git-send-email.adoc list items

Signed-off-by: Jean-Noël Avila <jn.avila@free.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-checkout.adoc

@@ -509,7 +509,7 @@ ARGUMENT DISAMBIGUATION
 -----------------------
 
 When you run `git checkout <something>`, Git tries to guess whether
-`<something>` is intended to be a branch, a commit, or a set of file(s),
+_<something>_ is intended to be a branch, a commit, or a set of file(s),
 and then either switches to that branch or commit, or restores the
 specified files.
 

Documentation/git-send-email.adoc

@@ -277,7 +277,7 @@ must be used for each option.
 --smtp-ssl::
 	Legacy alias for `--smtp-encryption ssl`.
 
---smtp-ssl-cert-path::
+--smtp-ssl-cert-path <path>::
 	Path to a store of trusted CA certificates for SMTP SSL/TLS
 	certificate validation (either a directory that has been processed
 	by `c_rehash`, or a single file containing one or more PEM format
@@ -510,12 +510,12 @@ have been specified, in which case default to `compose`.
 	Currently, validation means the following:
 +
 --
-		*	Invoke the sendemail-validate hook if present (see linkgit:githooks[5]).
-		*	Warn of patches that contain lines longer than
-			998 characters unless a suitable transfer encoding
-			(`auto`, `base64`, or `quoted-printable`) is used;
-			this is due to SMTP limits as described by
-			https://www.ietf.org/rfc/rfc5322.txt.
+* Invoke the sendemail-validate hook if present (see linkgit:githooks[5]).
+* Warn of patches that contain lines longer than
+  998 characters unless a suitable transfer encoding
+  (`auto`, `base64`, or `quoted-printable`) is used;
+  this is due to SMTP limits as described by
+  https://www.ietf.org/rfc/rfc5322.txt.
 --
 +
 Default is the value of `sendemail.validate`; if this is not set,

Documentation/git-worktree.adoc

@@ -104,7 +104,7 @@ associated with a new unborn branch named _<branch>_ (after
 passed to the command. In the event the repository has a remote and
 `--guess-remote` is used, but no remote or local branches exist, then the
 command fails with a warning reminding the user to fetch from their remote
-first (or override by using `-f/--force`).
+first (or override by using `-f`/`--force`).
 
 `list`::