feat(pdm): pdm-control LibraryPath + InstallDir

Two optional pdm-control fields:
- LibraryPath: true/false  — when true, pmm writes the package's lib dir to
  ~/.bashrc LD_LIBRARY_PATH so shared libs installed by PMM are found at runtime
  (per-package opt-in; default false so plain tools don't pollute the env).
- InstallDir: <subdir>     — install the package to ~/.pmm/root/<subdir> (its
  bin goes to <subdir>/bin and is added to PATH; <subdir>/lib is what
  LibraryPath points at).

Also ensure the target dir exists before tar -C. Updated ppdm.md tutorial.

src/pdm.c

@@ -540,6 +540,23 @@ int pdm_install_file(const char *pdmfile) {
         chdir_restore(); remove(tmpname); return -1;
     }
 
+    /* pdm-control knobs: LibraryPath (auto-add lib dir to LD_LIBRARY_PATH) and
+     * InstallDir (optional install subdir under the PMM root). */
+    pmm_libpath_wanted = 0;
+    pmm_install_subdir[0] = 0;
+    char *libp = control_get(ctl, "LibraryPath");
+    if (libp && libp[0]) { pmm_libpath_wanted = (strcmp(libp, "true") == 0 || strcmp(libp, "1") == 0); free(libp); }
+    char *inst = control_get(ctl, "InstallDir");
+    if (inst && *inst) {
+        /* keep it relative & safe (no .., no leading /) */
+        size_t il = strlen(inst);
+        if (il >= sizeof(pmm_install_subdir)) il = sizeof(pmm_install_subdir) - 1;
+        memcpy(pmm_install_subdir, inst, il); pmm_install_subdir[il] = 0;
+        for (char *q = pmm_install_subdir; *q; q++) if (*q == '\\') *q = '/';
+        if (pmm_install_subdir[0] == '/' || strstr(pmm_install_subdir, "..")) pmm_install_subdir[0] = 0;
+        free(inst);
+    }
+
     /* reject an install that would conflict with a package already present */
     char *confl = control_get(ctl, "Conflicts");
     if (confl && *confl && any_installed_conflict(confl)) {
@@ -551,6 +568,12 @@ int pdm_install_file(const char *pdmfile) {
 
     /* extract data into root (relative target: cwd is already the pm dir) */
     const char *tgt = flat ? "." : "root";
+    char tgtbuf[1400];
+    if (!flat && pmm_install_subdir[0]) {
+        snprintf(tgtbuf, sizeof(tgtbuf), "root/%s", pmm_install_subdir);
+        tgt = tgtbuf;
+    }
+    mkdir_p(tgt);               /* ensure the target dir exists before -C */
     /* If the package is pmm itself, its exe is the currently running binary and
      * Windows/locked images can't be overwritten by tar. Move it aside first so
      * the new binary can be written; restore on failure. */
@@ -622,6 +645,8 @@ int pdm_install_file(const char *pdmfile) {
     }
 
     pmm_add_to_path();  /* auto-put PMM dirs (e.g. root/nodejs) on PATH */
+    pmm_libpath_wanted = 0;      /* don't leak the LibraryPath/InstallDir to later installs */
+    pmm_install_subdir[0] = 0;
 
 #ifndef _WIN32
     /* On Linux/macOS, mark anything in <root>/bin executable. Windows doesn't

src/pmm.c

@@ -113,6 +113,10 @@ static const char *home_dir(void) {
 static char g_drive[4] = "";   /* "D", or "" = use home */
 static char g_base_path[1024] = ""; /* exact install base, or "" */
 
+/* Set by pdm_install_file from pdm-control (LibraryPath / InstallDir). */
+int pmm_libpath_wanted = 0;
+char pmm_install_subdir[256] = "";
+
 static const char *drive_state_path(char *buf, size_t size) {
     snprintf(buf, size, "%s/.pmm/install-drive", home_dir());
     return buf;
@@ -366,6 +370,17 @@ void pmm_add_to_path(void) {
     }
 #endif
 
+    /* A package may declare an install subdir (pdm-control InstallDir): also put
+     * its <subdir>/bin on PATH if it holds executables. */
+    if (pmm_install_subdir[0]) {
+        char subbin[1400];
+        snprintf(subbin, sizeof(subbin), "%s/%s/bin", base, pmm_install_subdir);
+        if (dir_has_exec(subbin)) add_path_candidate(list, &n, 160, subbin);
+        char subcmd[1400];
+        snprintf(subcmd, sizeof(subcmd), "%s/%s/cmd", base, pmm_install_subdir);
+        if (dir_has_exec(subcmd)) add_path_candidate(list, &n, 160, subcmd);
+    }
+
     /* read current user PATH */
     char cur[16384] = "";
 #ifdef _WIN32
@@ -435,14 +450,18 @@ void pmm_add_to_path(void) {
         if (f) {
             fprintf(f, "\n# PMM PATH\n");
             for (int i = 0; i < n; i++) if (list[i][0]) fprintf(f, "export PATH=\"%s:$PATH\"\n", list[i]);
-            /* Shared libraries installed by PMM live under <home>/root/lib;
-             * make them findable by dynamically-linked tools automatically. */
-            fprintf(f, "\n# PMM shared library path\n");
-            if (pmm_flat_mode())
-                fprintf(f, "export LD_LIBRARY_PATH=\"%s/lib:%LD_LIBRARY_PATH\"\n", home);
-            else
-                fprintf(f, "export LD_LIBRARY_PATH=\"%s/root/lib:%s/root/lib/x86_64-linux-gnu:$LD_LIBRARY_PATH\"\n",
-                        home, home);
+            /* If the package opted in (pdm-control: LibraryPath=true), make its
+             * lib dir findable by dynamically-linked tools automatically. */
+            if (pmm_libpath_wanted) {
+                char libdir[1400];
+                if (pmm_install_subdir[0])
+                    snprintf(libdir, sizeof(libdir), "%s/%s/lib", base, pmm_install_subdir);
+                else
+                    snprintf(libdir, sizeof(libdir), "%s/lib", base);
+                fprintf(f, "\n# PMM shared library path\n");
+                fprintf(f, "export LD_LIBRARY_PATH=\"%s:%s/x86_64-linux-gnu:$LD_LIBRARY_PATH\"\n",
+                        libdir, libdir);
+            }
             fclose(f);
         }
         (void)she;

src/pmm.h

@@ -9,6 +9,12 @@
  * On Windows persists via the user registry PATH; on Unix appends to shell rc. */
 void pmm_add_to_path(void);
 
+/* Set by the .pdm installer from pdm-control (LibraryPath/InstallDir) before
+ * calling pmm_add_to_path: whether to export the package's lib dir on
+ * LD_LIBRARY_PATH, and an optional install subdir under the PMM root. */
+extern int pmm_libpath_wanted;
+extern char pmm_install_subdir[256];
+
 /* Set the install location by drive letter ("D" -> D:\.pmm). An empty string
  * clears back to the user-home default. Persisted across runs. */
 void pmm_set_install_drive(const char *letter);

web/docs/md/ppdm.md

@@ -78,8 +78,14 @@ Version: 1.0.0
 Architecture: linux
 Description: My app
 Maintainer: you@mail.com
+# 可选:
+# LibraryPath: true   # 装到 ~/.pmm/root 后，自动把本包 lib/ 加入 LD_LIBRARY_PATH（新 shell 生效）
+# InstallDir: tools/myapp   # 把本包装到 ~/.pmm/root/tools/myapp (bin -> .../bin, lib -> .../lib)
 ```
 
+> `LibraryPath` 默认 `false`（不加）；`true` 时 pmm 会在 `~/.bashrc` 写入本包 lib 目录的
+> `LD_LIBRARY_PATH`。`InstallDir` 可把包装到 `~/.pmm/root/<子目录>`，该目录下的 `bin` 也会进 PATH。
+
 打包：
 
 ```bash