merge(third_party/git): Merge squashed git subtree at v2.23.0 r/373

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+git-cvsserver(1)
+================
+
+NAME
+----
+git-cvsserver - A CVS server emulator for Git
+
+SYNOPSIS
+--------
+
+SSH:
+
+[verse]
+export CVS_SERVER="git cvsserver"
+'cvs' -d :ext:user@server/path/repo.git co <HEAD_name>
+
+pserver (/etc/inetd.conf):
+
+[verse]
+cvspserver stream tcp nowait nobody /usr/bin/git-cvsserver git-cvsserver pserver
+
+Usage:
+
+[verse]
+'git-cvsserver' [<options>] [pserver|server] [<directory> ...]
+
+OPTIONS
+-------
+
+All these options obviously only make sense if enforced by the server side.
+They have been implemented to resemble the linkgit:git-daemon[1] options as
+closely as possible.
+
+--base-path <path>::
+Prepend 'path' to requested CVSROOT
+
+--strict-paths::
+Don't allow recursing into subdirectories
+
+--export-all::
+Don't check for `gitcvs.enabled` in config. You also have to specify a list
+of allowed directories (see below) if you want to use this option.
+
+-V::
+--version::
+Print version information and exit
+
+-h::
+-H::
+--help::
+Print usage information and exit
+
+<directory>::
+You can specify a list of allowed directories. If no directories
+are given, all are allowed. This is an additional restriction, gitcvs
+access still needs to be enabled by the `gitcvs.enabled` config option
+unless `--export-all` was given, too.
+
+
+DESCRIPTION
+-----------
+
+This application is a CVS emulation layer for Git.
+
+It is highly functional. However, not all methods are implemented,
+and for those methods that are implemented,
+not all switches are implemented.
+
+Testing has been done using both the CLI CVS client, and the Eclipse CVS
+plugin. Most functionality works fine with both of these clients.
+
+LIMITATIONS
+-----------
+
+CVS clients cannot tag, branch or perform Git merges.
+
+'git-cvsserver' maps Git branches to CVS modules. This is very different
+from what most CVS users would expect since in CVS modules usually represent
+one or more directories.
+
+INSTALLATION
+------------
+
+1. If you are going to offer CVS access via pserver, add a line in
+   /etc/inetd.conf like
++
+--
+------
+   cvspserver stream tcp nowait nobody git-cvsserver pserver
+
+------
+Note: Some inetd servers let you specify the name of the executable
+independently of the value of argv[0] (i.e. the name the program assumes
+it was executed with). In this case the correct line in /etc/inetd.conf
+looks like
+
+------
+   cvspserver stream tcp nowait nobody /usr/bin/git-cvsserver git-cvsserver pserver
+
+------
+
+Only anonymous access is provided by pserve by default. To commit you
+will have to create pserver accounts, simply add a gitcvs.authdb
+setting in the config file of the repositories you want the cvsserver
+to allow writes to, for example:
+
+------
+
+   [gitcvs]
+	authdb = /etc/cvsserver/passwd
+
+------
+The format of these files is username followed by the encrypted password,
+for example:
+
+------
+   myuser:$1Oyx5r9mdGZ2
+   myuser:$1$BA)@$vbnMJMDym7tA32AamXrm./
+------
+You can use the 'htpasswd' facility that comes with Apache to make these
+files, but Apache's MD5 crypt method differs from the one used by most C
+library's crypt() function, so don't use the -m option.
+
+Alternatively you can produce the password with perl's crypt() operator:
+-----
+   perl -e 'my ($user, $pass) = @ARGV; printf "%s:%s\n", $user, crypt($user, $pass)' $USER password
+-----
+
+Then provide your password via the pserver method, for example:
+------
+   cvs -d:pserver:someuser:somepassword <at> server/path/repo.git co <HEAD_name>
+------
+No special setup is needed for SSH access, other than having Git tools
+in the PATH. If you have clients that do not accept the CVS_SERVER
+environment variable, you can rename 'git-cvsserver' to `cvs`.
+
+Note: Newer CVS versions (>= 1.12.11) also support specifying
+CVS_SERVER directly in CVSROOT like
+
+------
+cvs -d ":ext;CVS_SERVER=git cvsserver:user@server/path/repo.git" co <HEAD_name>
+------
+This has the advantage that it will be saved in your 'CVS/Root' files and
+you don't need to worry about always setting the correct environment
+variable.  SSH users restricted to 'git-shell' don't need to override the default
+with CVS_SERVER (and shouldn't) as 'git-shell' understands `cvs` to mean
+'git-cvsserver' and pretends that the other end runs the real 'cvs' better.
+--
+2. For each repo that you want accessible from CVS you need to edit config in
+   the repo and add the following section.
++
+--
+------
+   [gitcvs]
+        enabled=1
+        # optional for debugging
+	logFile=/path/to/logfile
+
+------
+Note: you need to ensure each user that is going to invoke 'git-cvsserver' has
+write access to the log file and to the database (see
+<<dbbackend,Database Backend>>. If you want to offer write access over
+SSH, the users of course also need write access to the Git repository itself.
+
+You also need to ensure that each repository is "bare" (without a Git index
+file) for `cvs commit` to work. See linkgit:gitcvs-migration[7].
+
+[[configaccessmethod]]
+All configuration variables can also be overridden for a specific method of
+access. Valid method names are "ext" (for SSH access) and "pserver". The
+following example configuration would disable pserver access while still
+allowing access over SSH.
+------
+   [gitcvs]
+        enabled=0
+
+   [gitcvs "ext"]
+        enabled=1
+------
+--
+3. If you didn't specify the CVSROOT/CVS_SERVER directly in the checkout command,
+   automatically saving it in your 'CVS/Root' files, then you need to set them
+   explicitly in your environment.  CVSROOT should be set as per normal, but the
+   directory should point at the appropriate Git repo.  As above, for SSH clients
+   _not_ restricted to 'git-shell', CVS_SERVER should be set to 'git-cvsserver'.
++
+--
+------
+     export CVSROOT=:ext:user@server:/var/git/project.git
+     export CVS_SERVER="git cvsserver"
+------
+--
+4. For SSH clients that will make commits, make sure their server-side
+   .ssh/environment files (or .bashrc, etc., according to their specific shell)
+   export appropriate values for GIT_AUTHOR_NAME, GIT_AUTHOR_EMAIL,
+   GIT_COMMITTER_NAME, and GIT_COMMITTER_EMAIL.  For SSH clients whose login
+   shell is bash, .bashrc may be a reasonable alternative.
+
+5. Clients should now be able to check out the project. Use the CVS 'module'
+   name to indicate what Git 'head' you want to check out.  This also sets the
+   name of your newly checked-out directory, unless you tell it otherwise with
+   `-d <dir_name>`.  For example, this checks out 'master' branch to the
+   `project-master` directory:
++
+------
+     cvs co -d project-master master
+------
+
+[[dbbackend]]
+DATABASE BACKEND
+----------------
+
+'git-cvsserver' uses one database per Git head (i.e. CVS module) to
+store information about the repository to maintain consistent
+CVS revision numbers. The database needs to be
+updated (i.e. written to) after every commit.
+
+If the commit is done directly by using `git` (as opposed to
+using 'git-cvsserver') the update will need to happen on the
+next repository access by 'git-cvsserver', independent of
+access method and requested operation.
+
+That means that even if you offer only read access (e.g. by using
+the pserver method), 'git-cvsserver' should have write access to
+the database to work reliably (otherwise you need to make sure
+that the database is up to date any time 'git-cvsserver' is executed).
+
+By default it uses SQLite databases in the Git directory, named
+`gitcvs.<module_name>.sqlite`. Note that the SQLite backend creates
+temporary files in the same directory as the database file on
+write so it might not be enough to grant the users using
+'git-cvsserver' write access to the database file without granting
+them write access to the directory, too.
+
+The database cannot be reliably regenerated in a
+consistent form after the branch it is tracking has changed.
+Example: For merged branches, 'git-cvsserver' only tracks
+one branch of development, and after a 'git merge' an
+incrementally updated database may track a different branch
+than a database regenerated from scratch, causing inconsistent
+CVS revision numbers. `git-cvsserver` has no way of knowing which
+branch it would have picked if it had been run incrementally
+pre-merge. So if you have to fully or partially (from old
+backup) regenerate the database, you should be suspicious
+of pre-existing CVS sandboxes.
+
+You can configure the database backend with the following
+configuration variables:
+
+Configuring database backend
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+'git-cvsserver' uses the Perl DBI module. Please also read
+its documentation if changing these variables, especially
+about `DBI->connect()`.
+
+gitcvs.dbName::
+	Database name. The exact meaning depends on the
+	selected database driver, for SQLite this is a filename.
+	Supports variable substitution (see below). May
+	not contain semicolons (`;`).
+	Default: '%Ggitcvs.%m.sqlite'
+
+gitcvs.dbDriver::
+	Used DBI driver. You can specify any available driver
+	for this here, but it might not work. cvsserver is tested
+	with 'DBD::SQLite', reported to work with
+	'DBD::Pg', and reported *not* to work with 'DBD::mysql'.
+	Please regard this as an experimental feature. May not
+	contain colons (`:`).
+	Default: 'SQLite'
+
+gitcvs.dbuser::
+	Database user. Only useful if setting `dbDriver`, since
+	SQLite has no concept of database users. Supports variable
+	substitution (see below).
+
+gitcvs.dbPass::
+	Database password.  Only useful if setting `dbDriver`, since
+	SQLite has no concept of database passwords.
+
+gitcvs.dbTableNamePrefix::
+	Database table name prefix.  Supports variable substitution
+	(see below).  Any non-alphabetic characters will be replaced
+	with underscores.
+
+All variables can also be set per access method, see <<configaccessmethod,above>>.
+
+Variable substitution
+^^^^^^^^^^^^^^^^^^^^^
+In `dbDriver` and `dbUser` you can use the following variables:
+
+%G::
+	Git directory name
+%g::
+	Git directory name, where all characters except for
+	alpha-numeric ones, `.`, and `-` are replaced with
+	`_` (this should make it easier to use the directory
+	name in a filename if wanted)
+%m::
+	CVS module/Git head name
+%a::
+	access method (one of "ext" or "pserver")
+%u::
+	Name of the user running 'git-cvsserver'.
+	If no name can be determined, the
+	numeric uid is used.
+
+ENVIRONMENT
+-----------
+
+These variables obviate the need for command-line options in some
+circumstances, allowing easier restricted usage through git-shell.
+
+GIT_CVSSERVER_BASE_PATH takes the place of the argument to --base-path.
+
+GIT_CVSSERVER_ROOT specifies a single-directory whitelist. The
+repository must still be configured to allow access through
+git-cvsserver, as described above.
+
+When these environment variables are set, the corresponding
+command-line arguments may not be used.
+
+ECLIPSE CVS CLIENT NOTES
+------------------------
+
+To get a checkout with the Eclipse CVS client:
+
+1. Select "Create a new project -> From CVS checkout"
+2. Create a new location. See the notes below for details on how to choose the
+   right protocol.
+3. Browse the 'modules' available. It will give you a list of the heads in
+   the repository. You will not be able to browse the tree from there. Only
+   the heads.
+4. Pick `HEAD` when it asks what branch/tag to check out. Untick the
+   "launch commit wizard" to avoid committing the .project file.
+
+Protocol notes: If you are using anonymous access via pserver, just select that.
+Those using SSH access should choose the 'ext' protocol, and configure 'ext'
+access on the Preferences->Team->CVS->ExtConnection pane. Set CVS_SERVER to
+"`git cvsserver`". Note that password support is not good when using 'ext',
+you will definitely want to have SSH keys setup.
+
+Alternatively, you can just use the non-standard extssh protocol that Eclipse
+offer. In that case CVS_SERVER is ignored, and you will have to replace
+the cvs utility on the server with 'git-cvsserver' or manipulate your `.bashrc`
+so that calling 'cvs' effectively calls 'git-cvsserver'.
+
+CLIENTS KNOWN TO WORK
+---------------------
+
+- CVS 1.12.9 on Debian
+- CVS 1.11.17 on MacOSX (from Fink package)
+- Eclipse 3.0, 3.1.2 on MacOSX (see Eclipse CVS Client Notes)
+- TortoiseCVS
+
+OPERATIONS SUPPORTED
+--------------------
+
+All the operations required for normal use are supported, including
+checkout, diff, status, update, log, add, remove, commit.
+
+Most CVS command arguments that read CVS tags or revision numbers
+(typically -r) work, and also support any git refspec
+(tag, branch, commit ID, etc).
+However, CVS revision numbers for non-default branches are not well
+emulated, and cvs log does not show tags or branches at
+all.  (Non-main-branch CVS revision numbers superficially resemble CVS
+revision numbers, but they actually encode a git commit ID directly,
+rather than represent the number of revisions since the branch point.)
+
+Note that there are two ways to checkout a particular branch.
+As described elsewhere on this page, the "module" parameter
+of cvs checkout is interpreted as a branch name, and it becomes
+the main branch.  It remains the main branch for a given sandbox
+even if you temporarily make another branch sticky with
+cvs update -r.  Alternatively, the -r argument can indicate
+some other branch to actually checkout, even though the module
+is still the "main" branch.  Tradeoffs (as currently
+implemented): Each new "module" creates a new database on disk with
+a history for the given module, and after the database is created,
+operations against that main branch are fast.  Or alternatively,
+-r doesn't take any extra disk space, but may be significantly slower for
+many operations, like cvs update.
+
+If you want to refer to a git refspec that has characters that are
+not allowed by CVS, you have two options.  First, it may just work
+to supply the git refspec directly to the appropriate CVS -r argument;
+some CVS clients don't seem to do much sanity checking of the argument.
+Second, if that fails, you can use a special character escape mechanism
+that only uses characters that are valid in CVS tags.  A sequence
+of 4 or 5 characters of the form (underscore (`"_"`), dash (`"-"`),
+one or two characters, and dash (`"-"`)) can encode various characters based
+on the one or two letters: `"s"` for slash (`"/"`), `"p"` for
+period (`"."`), `"u"` for underscore (`"_"`), or two hexadecimal digits
+for any byte value at all (typically an ASCII number, or perhaps a part
+of a UTF-8 encoded character).
+
+Legacy monitoring operations are not supported (edit, watch and related).
+Exports and tagging (tags and branches) are not supported at this stage.
+
+CRLF Line Ending Conversions
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+By default the server leaves the `-k` mode blank for all files,
+which causes the CVS client to treat them as a text files, subject
+to end-of-line conversion on some platforms.
+
+You can make the server use the end-of-line conversion attributes to
+set the `-k` modes for files by setting the `gitcvs.usecrlfattr`
+config variable.  See linkgit:gitattributes[5] for more information
+about end-of-line conversion.
+
+Alternatively, if `gitcvs.usecrlfattr` config is not enabled
+or the attributes do not allow automatic detection for a filename, then
+the server uses the `gitcvs.allBinary` config for the default setting.
+If `gitcvs.allBinary` is set, then file not otherwise
+specified will default to '-kb' mode. Otherwise the `-k` mode
+is left blank. But if `gitcvs.allBinary` is set to "guess", then
+the correct `-k` mode will be guessed based on the contents of
+the file.
+
+For best consistency with 'cvs', it is probably best to override the
+defaults by setting `gitcvs.usecrlfattr` to true,
+and `gitcvs.allBinary` to "guess".
+
+DEPENDENCIES
+------------
+'git-cvsserver' depends on DBD::SQLite.
+
+GIT
+---
+Part of the linkgit:git[1] suite