SYNOPSIS
--------
-'git-mktag'
+'git-mktag' < signature_file
DESCRIPTION
-----------
-Reads a tag contents from its standard input and creates a tag object.
-The input must be a well formed tag object.
+Reads a tag contents on standard input and creates a tag object
+that can also be used to sign other objects.
+
+The output is the new tag's <object> identifier.
+
+Tag Format
+----------
+A tag signature file has a very simple fixed format: three lines of
+
+ object <sha1>
+ type <typename>
+ tag <tagname>
+
+followed by some 'optional' free-form signature that git itself
+doesn't care about, but that can be verified with gpg or similar.
+
+The size of the full object is artificially limited to 8kB. (Just
+because I'm a lazy bastard, and if you can't fit a signature in that
+size, you're doing something wrong)
Author
Indicates a filename - always relative to the root of
the tree structure GIT_INDEX_FILE describes.
+Symbolic Identifiers
+--------------------
+Any git comand accepting any <object> can also use the following symbolic notation:
+
+HEAD::
+ indicates the head of the repository (ie the contents of `$GIT_DIR/HEAD`)
+<tag>::
+ a valid tag 'name'+
+ (ie the contents of `$GIT_DIR/refs/tags/<tag>`)
+<head>::
+ a valid head 'name'+
+ (ie the contents of `$GIT_DIR/refs/heads/<head>`)
+<snap>::
+ a valid snapshot 'name'+
+ (ie the contents of `$GIT_DIR/refs/snap/<snap>`)
+
+
+File/Directory Structure
+------------------------
+The git-core manipulates the following areas in the directory:
+
+ .git/ The base (overridden with $GIT_DIR)
+ objects/ The object base (overridden with $GIT_OBJECT_DIRECTORY)
+ ??/ 'First 2 chars of object' directories
+
+It can interrogate (but never updates) the following areas:
+
+ refs/ Directories containing symbolic names for objects
+ (each file contains the hex SHA1 + newline)
+ heads/ Commits which are heads of various sorts
+ tags/ Tags, by the tag name (or some local renaming of it)
+ snap/ ????
+ ... Everything else isn't shared
+ HEAD Symlink to refs/heads/<something>
+
+Higher level SCMs may provide and manage additional information in the
+GIT_DIR.
+
Terminology
-----------
Each line contains terms used interchangeably
---------------------
Various git commands use the following environment variables:
-- 'GIT_AUTHOR_NAME'
-- 'GIT_AUTHOR_EMAIL'
-- 'GIT_AUTHOR_DATE'
-- 'GIT_COMMITTER_NAME'
-- 'GIT_COMMITTER_EMAIL'
-- 'GIT_DIFF_OPTS'
-- 'GIT_EXTERNAL_DIFF'
-- 'GIT_INDEX_FILE'
-- 'GIT_OBJECT_DIRECTORY'
-- 'GIT_ALTERNATE_OBJECT_DIRECTORIES'
-
+The git Repository
+~~~~~~~~~~~~~~~~~~
+These environment variables apply to 'all' core git commands. Nb: it
+is worth noting that they may be used/overridden by SCMS sitting above
+git so take care if using Cogito etc
+
+'GIT_INDEX_FILE'::
+ This environment allows the specification of an alternate
+ cache/index file. If not specified, the default of
+ `$GIT_DIR/index` is used.
+
+'GIT_OBJECT_DIRECTORY'::
+ If the object storage directory is specified via this
+ environment variable then the sha1 directories are created
+ underneath - otherwise the default `$GIT_DIR/objects`
+ directory is used.
+
+'GIT_ALTERNATE_OBJECT_DIRECTORIES'::
+ Due to the immutable nature of git objects, old objects can be
+ archived into shared, read-only directories. This variable
+ specifies a ":" seperated list of git object directories which
+ can be used to search for git objects. New objects will not be
+ written to these directories.
+
+'GIT_DIR'::
+ If the 'GIT_DIR' environment variable is set then it specifies
+ a path to use instead of `./.git` for the base of the
+ repository.
+
+git Commits
+~~~~~~~~~~~
+'GIT_AUTHOR_NAME'::
+'GIT_AUTHOR_EMAIL'::
+'GIT_AUTHOR_DATE'::
+'GIT_COMMITTER_NAME'::
+'GIT_COMMITTER_EMAIL'::
+ see link:git-commit-tree.html[git-commit-tree]
+
+git Diffs
+~~~~~~~~~
+GIT_DIFF_OPTS::
+GIT_EXTERNAL_DIFF::
+ see the "generating patches" section in :
+ link:git-diff-cache.html[git-diff-cache];
+ link:git-diff-files.html[git-diff-files];
+ link:git-diff-tree.html[git-diff-tree]
Author
------