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<div id="header">
<h1>Long-running process protocol</h1>
<span id="revdate"></span>
</div>
<div id="content">
<div id="preamble">
<div class="sectionbody">
<div class="paragraph"><p>This protocol is used when Git needs to communicate with an external
process throughout the entire life of a single Git command. All
communication is in pkt-line format (see <a href="../gitprotocol-common.html">gitprotocol-common(5)</a>)
over standard input and standard output.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_handshake">Handshake</h2>
<div class="sectionbody">
<div class="paragraph"><p>Git starts by sending a welcome message (for example,
"git-filter-client"), a list of supported protocol version numbers, and
a flush packet. Git expects to read the welcome message with "server"
instead of "client" (for example, "git-filter-server"), exactly one
protocol version number from the previously sent list, and a flush
packet. All further communication will be based on the selected version.
The remaining protocol description below documents "version=2". Please
note that "version=42" in the example below does not exist and is only
there to illustrate how the protocol would look like with more than one
version.</p></div>
<div class="paragraph"><p>After the version negotiation Git sends a list of all capabilities that
it supports and a flush packet. Git expects to read a list of desired
capabilities, which must be a subset of the supported capabilities list,
and a flush packet as response:</p></div>
<div class="listingblock">
<div class="content">
<pre><code>packet:          git&gt; git-filter-client
packet:          git&gt; version=2
packet:          git&gt; version=42
packet:          git&gt; 0000
packet:          git&lt; git-filter-server
packet:          git&lt; version=2
packet:          git&lt; 0000
packet:          git&gt; capability=clean
packet:          git&gt; capability=smudge
packet:          git&gt; capability=not-yet-invented
packet:          git&gt; 0000
packet:          git&lt; capability=clean
packet:          git&lt; capability=smudge
packet:          git&lt; 0000</code></pre>
</div></div>
</div>
</div>
<div class="sect1">
<h2 id="_shutdown">Shutdown</h2>
<div class="sectionbody">
<div class="paragraph"><p>Git will close
the command pipe on exit. The filter is expected to detect EOF
and exit gracefully on its own. Git will wait until the filter
process has stopped.</p></div>
</div>
</div>
</div>
<div id="footnotes"><hr /></div>
<div id="footer">
<div id="footer-text">
Last updated
 2025-06-13 22:14:31 UTC
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