Reify the git environment at compile time into the code

Use it to output a minimal `./tezos-node --version`

Works both when you compile inside a git repository or from an
archive generated by `git archive` (which is what gitlab does when
you click on "Download zip/tar.gz/tar.bz2" in the web interface)

.gitattributes

@@ -0,0 +1,4 @@
+.gitignore	export-ignore
+.gitattributes	export-ignore
+.gitlab-ci.yml	export-ignore
+src/lib_base/current_git_info.ml	export-subst

src/bin_node/main.ml

@@ -51,9 +51,13 @@ let man =
   Node_run_command.Manpage.examples
 
 let info =
+  let version =
+    Tezos_base.Current_git_info.abbreviated_commit_hash ^
+    " ("^Tezos_base.Current_git_info.committer_date^")" in
   Cmdliner.Term.info
     ~doc:"The Tezos node"
     ~man
+    ~version
     "tezos-node"
 
 let commands = [

src/lib_base/current_git_info.ml

@@ -0,0 +1,45 @@
+(*****************************************************************************)
+(*                                                                           *)
+(* Open Source License                                                       *)
+(* Copyright (c) 2019 Nomadic Labs, <contact@nomadic-labs.com>               *)
+(*                                                                           *)
+(* Permission is hereby granted, free of charge, to any person obtaining a   *)
+(* copy of this software and associated documentation files (the "Software"),*)
+(* to deal in the Software without restriction, including without limitation *)
+(* the rights to use, copy, modify, merge, publish, distribute, sublicense,  *)
+(* and/or sell copies of the Software, and to permit persons to whom the     *)
+(* Software is furnished to do so, subject to the following conditions:      *)
+(*                                                                           *)
+(* The above copyright notice and this permission notice shall be included   *)
+(* in all copies or substantial portions of the Software.                    *)
+(*                                                                           *)
+(* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR*)
+(* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,  *)
+(* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL   *)
+(* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER*)
+(* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING   *)
+(* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER       *)
+(* DEALINGS IN THE SOFTWARE.                                                 *)
+(*                                                                           *)
+(*****************************************************************************)
+
+let raw_commit_hash = "$Format:%H$"
+
+let commit_hash =
+  if String.equal raw_commit_hash ("$Format:"^"%H$"(*trick to avoid git-subst*))
+  then Generated_git_info.commit_hash
+  else raw_commit_hash
+
+let raw_abbreviated_commit_hash = "$Format:%h$"
+
+let abbreviated_commit_hash =
+  if String.equal raw_abbreviated_commit_hash ("$Format:"^"%h$")
+  then Generated_git_info.abbreviated_commit_hash
+  else raw_abbreviated_commit_hash
+
+let raw_committer_date = "$Format:%ci$"
+
+let committer_date =
+  if String.equal raw_committer_date ("$Format:"^"%ci$")
+  then Generated_git_info.committer_date
+  else raw_committer_date

src/lib_base/current_git_info.mli

@@ -0,0 +1,28 @@
+(*****************************************************************************)
+(*                                                                           *)
+(* Open Source License                                                       *)
+(* Copyright (c) 2019 Nomadic Labs, <contact@nomadic-labs.com>               *)
+(*                                                                           *)
+(* Permission is hereby granted, free of charge, to any person obtaining a   *)
+(* copy of this software and associated documentation files (the "Software"),*)
+(* to deal in the Software without restriction, including without limitation *)
+(* the rights to use, copy, modify, merge, publish, distribute, sublicense,  *)
+(* and/or sell copies of the Software, and to permit persons to whom the     *)
+(* Software is furnished to do so, subject to the following conditions:      *)
+(*                                                                           *)
+(* The above copyright notice and this permission notice shall be included   *)
+(* in all copies or substantial portions of the Software.                    *)
+(*                                                                           *)
+(* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR*)
+(* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,  *)
+(* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL   *)
+(* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER*)
+(* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING   *)
+(* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER       *)
+(* DEALINGS IN THE SOFTWARE.                                                 *)
+(*                                                                           *)
+(*****************************************************************************)
+
+val commit_hash : string
+val abbreviated_commit_hash : string
+val committer_date : string

src/lib_base/dune

@@ -1,6 +1,7 @@
 (library
  (name tezos_base)
  (public_name tezos-base)
+ (modules :standard \ Get-git-info)
  (flags (:standard -w -30
                    -open Tezos_stdlib
                    -open Tezos_crypto
@@ -24,6 +25,11 @@
             mtime.clock.os
             ipaddr.unix))
 
+(rule
+    (targets generated_git_info.ml)
+    (deps get-git-info.ml)
+    (action (with-stdout-to %{targets} (run %{ocaml} unix.cma %{deps}))))
+
 (alias
  (name runtest_indent)
  (deps (glob_files *.ml{,i}))

src/lib_base/get-git-info.ml

@@ -0,0 +1,19 @@
+#!/usr/bin/env ocaml
+
+               #load "unix.cma"
+
+let query cmd =
+  let chan = Unix.open_process_in cmd in
+  try
+    let out = input_line chan in
+    if Unix.close_process_in chan = Unix.WEXITED 0 then out
+    else "unkown"
+  with End_of_file -> "unkown"
+
+let () =
+  Format.printf "@[<v>let commit_hash = \"%s\"@,"
+    (query "git show -s --pretty=format:%H");
+  Format.printf "let abbreviated_commit_hash = \"%s\"@,"
+    (query "git show -s --pretty=format:%h");
+  Format.printf "let committer_date = \"%s\"@]@."
+    (query "git show -s --pretty=format:%ci")