Add JANET_GIT to jpm.

This should allow work arounds for some windows installs.
Also, be clever about finding the location of te current git
executable on windows to avoid some path issues that seem to
occur on some windows installations.

CHANGELOG.md

@@ -2,6 +2,7 @@
 All notable changes to this project will be documented in this file.
 
 ## Unreleased - ???
+- Add JANET_GIT environment variable to jpm to use a specific git binary (useful mainly on windows).
 - `asm` and `disasm` functions now use keywords instead of macros for keys. Also
   some slight changes to the way constants are encoded (remove wrapping `quote` in some cases).
 - Expose current macro form inside macros as (dyn :macro-form)

jpm

@@ -647,6 +647,19 @@ int main(int argc, const char **argv) {
 # Installation and Dependencies
 #
 
+(var- stored-git-path nil)
+(defn- git-path
+    "Get the location of git such that it can be passed as an argument to os/execute."
+    "(Some builds/configurations of windows don't like just the string 'git')"
+    []
+    (if stored-git-path (break stored-git-path))
+    (set stored-git-path
+         (if is-win
+           (or (os/getenv "JANET_GIT") (pslurp "where git"))
+           (os/getenv "JANET_GIT" "git"))))
+
+(if is-win (pslurp "where git") "git"))
+
 (defn uninstall
   "Uninstall bundle named name"
   [name]
@@ -707,11 +720,11 @@ int main(int argc, const char **argv) {
                 :binpath (abspath (dyn :binpath JANET_BINPATH))]
       (os/cd module-dir)
       (unless fresh
-        (os/execute ["git" "pull" "origin" "master"] :p))
+        (os/execute [(git-path) "pull" "origin" "master"] :p))
       (when tag
-        (os/execute ["git" "reset" "--hard" tag] :p))
+        (os/execute [(git-path) "reset" "--hard" tag] :p))
       (unless (dyn :offline)
-        (os/execute ["git" "submodule" "update" "--init" "--recursive"] :p))
+        (os/execute [(git-path) "submodule" "update" "--init" "--recursive"] :p))
       (import-rules "./project.janet")
       (unless no-deps (do-rule "install-deps"))
       (do-rule "build")
@@ -955,8 +968,8 @@ int main(int argc, const char **argv) {
   (phony "manifest" []
          (print "generating " manifest "...")
          (mkdir manifests)
-         (def sha (pslurp "git rev-parse HEAD"))
-         (def url (pslurp "git remote get-url origin"))
+         (def sha (pslurp (string "\"" (git-path) "\" rev-parse HEAD")))
+         (def url (pslurp (string "\"" (git-path) "\" remote get-url origin"))
          (def man
            {:sha (if-not (empty? sha) sha)
             :repo (if-not (empty? url) url)

jpm.1

@@ -237,5 +237,10 @@ The git repository URL that contains a listing of packages. This allows installi
 is mostly a convenience. However, package dependencies can use short names, package listings
 can be used to choose a particular set of dependency versions for a whole project.
 
+.B JANET_GIT
+.RS
+An optional path to a git executable to use to clone git dependencies. By default, uses "git" on the current $PATH. You shouldn't need to set this
+if you have a normal install of git.
+
 .SH AUTHOR
 Written by Calvin Rose <calsrose@gmail.com>

src/core/os.c

@@ -339,7 +339,7 @@ static Janet os_execute(int32_t argc, Janet *argv) {
 
     JanetBuffer *buf = os_exec_escape(exargs);
     if (buf->count > 8191) {
-        janet_panic("command line string too long");
+        janet_panic("command line string too long (max 8191 characters)");
     }
     const char *path = (const char *) janet_unwrap_string(exargs.items[0]);
     char *cargv[2] = {(char *) buf->data, NULL};