doc: use 'title' consistently

The first line of a commit message is variously called 'title' or
'subject'.

Prefer 'title' unless discussing email.

Signed-off-by: M Hickford <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: hickford

Documentation/git-commit.txt

@@ -98,16 +98,16 @@ OPTIONS
 	replaces the log message of _<commit>_ with its own log message
 	but makes no changes to the content of _<commit>_.
 +
-The commit created by plain `--fixup=<commit>` has a subject
-composed of "fixup!" followed by the subject line from _<commit>_,
+The commit created by plain `--fixup=<commit>` has a title
+composed of "fixup!" followed by the title of _<commit>_,
 and is recognized specially by `git rebase --autosquash`. The `-m`
 option may be used to supplement the log message of the created
 commit, but the additional commentary will be thrown away once the
 "fixup!" commit is squashed into _<commit>_ by
 `git rebase --autosquash`.
 +
 The commit created by `--fixup=amend:<commit>` is similar but its
-subject is instead prefixed with "amend!". The log message of
+title is instead prefixed with "amend!". The log message of
 _<commit>_ is copied into the log message of the "amend!" commit and
 opened in an editor so it can be refined. When `git rebase
 --autosquash` squashes the "amend!" commit into _<commit>_, the
@@ -128,7 +128,7 @@ See linkgit:git-rebase[1] for details.
 
 `--squash=<commit>`::
 	Construct a commit message for use with `git rebase --autosquash`.
-	The commit message subject line is taken from the specified
+	The commit message title is taken from the specified
 	commit with a prefix of "squash! ".  Can be used with additional
 	commit message options (`-m`/`-c`/`-C`/`-F`). See
 	linkgit:git-rebase[1] for details.

Documentation/git-rebase.txt

@@ -599,11 +599,11 @@ See also INCOMPATIBLE OPTIONS below.
 --no-autosquash::
 	Automatically squash commits with specially formatted messages into
 	previous commits being rebased.  If a commit message starts with
-	"squash! ", "fixup! " or "amend! ", the remainder of the subject line
+	"squash! ", "fixup! " or "amend! ", the remainder of the title
 	is taken as a commit specifier, which matches a previous commit if it
-	matches the subject line or the hash of that commit.  If no commit
+	matches the title or the hash of that commit.  If no commit
 	matches fully, matches of the specifier with the start of commit
-	subjects are considered.
+	titles are considered.
 +
 In the rebase todo list, the actions of squash, fixup and amend commits are
 changed from `pick` to `squash`, `fixup` or `fixup -C`, respectively, and they
@@ -613,7 +613,7 @@ be used to review and edit the todo list before proceeding.
 The recommended way to create commits with squash markers is by using the
 `--squash`, `--fixup`, `--fixup=amend:` or `--fixup=reword:` options of
 linkgit:git-commit[1], which take the target commit as an argument and
-automatically fill in the subject line of the new commit from that.
+automatically fill in the title of the new commit from that.
 +
 Setting configuration variable `rebase.autoSquash` to true enables
 auto-squashing by default for interactive rebase.  The `--no-autosquash`